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Topics - Jetaholic

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Jet Pumps / SAFETY THREAD: Nozzle Hinge Pins
« on: September 06, 2008, 01:10:56 PM »
The most important part on any jet boat, yet probably the most neglected part on them as well. ALWAYS...and I mean ALWAYS...check the tightness on your nozzle bolts prior to launching. All it takes is an allen wrench and about 10 - 15 seconds.

The nozzle, aside from the throttle, is your only form of control on a jet boat. Not sure if any of you remember, but several years back there was a jet boat being used as a competition ski boat that ended up in the grand stands. People were injured badly and I think a few were killed. Well, investigation revealed that the tiller pin had fallen out because the maintenance crew had failed to check the bolts on them.

All because of someone else's negligence people were hurt and killed.

Guys, those pins are your life. Those pins are someone else's life. One of those pins ends up missing, you now compromise the controlability of that boat. Once the controlability is compromised, so is the safety of yourself as the driver, as well as your passengers and others around you. No tiller pin, no steering. No reverse pin, no brakes. It's that simple.

So everytime you launch, ALWAYS remember to check your nozzle pin bolts. It could mean your life. It can also mean someone else's life.

Engine Mechanical / Electrical / The Low Down On BBC Heads
« on: January 29, 2008, 04:15:25 PM »
There seems to be some confusion about the different head types used on Chevy Rat motors. Some people think there are only "oval" or "rectangular" ports, and some people don't understand the deal with "open" vs. "closed" chamber heads. This article, taken from the book by Ed Staffel "How To Build Max Performance Chevy Rat Motors", should help to explain the differences.

Small Oval Port (i.e. "peanut" port) heads

"Mark IV, Gen V and Gen VI small oval port cast iron heads, commonly called "truck", "round" or "peanut" ports and made from 1976 on, make power and high torque at very low RPM's and are helpful when the motor is pulling heavy loads in trucks, trailers or RV's. The velocity of air/fuel mixture in these heads is very high at low engine speeds, however they run out of breath at RPMs above 5,000 and are not really suitable for street performance or race applications, although larger valves, bowl and other port work can improve the flow situation. Small oval port heads have intake valves that are 2.06" in size, with 1.72" exhaust valves. They have hardened valve seats. These heads can have closed or open chambers (small or large chambers respectively). Most are found on trucks including late models, but there were some full size passenger cars and station wagons in the mid-70s that could be ordered with a 454 and may have the small oval port heads."

Large Oval Port Heads

"Mark IV large oval port heads make their power over a broader and higher RPM range. They are found on cars and trucks from 1965 through 1990 and make excellent street performance heads. They can be used on bracket drag race motors, after bowl porting and installation of bigger valves, with great results because they make a large amount of torque and will breathe well to about 6500RPM. They come with 2.06" intake and 1.72" exhaust valves. They have closed or open combustion chambers, and depending on when they were made have either soft or hardened valve seats. The open chamber style castings will flow more air than the closed chamber designs. This is due mainly to less valve shrouding. The downside with open chamber heads is that you will have to run a dome top piston to get any level of compression ratio above 8.5:1.

A good starting place would be cast iron, large oval port, open chamber casting #'s '781', '049', '359' or '241'. In 1996, Chevy introduced an over the counter aluminum open chamber head with large oval ports. This is the first factory big block aluminum head with large oval ports. This head will fit and seal with Mark IV, Gen V and Gen VI blocks.

Rectangular Port Heads

"Rectangular or 'square' port cast iron and aluminum cylinder heads are strictly for high-performance use. Because the intake port dimensions are so large, air/fuel velocities are at a low speed in the ports until the RPM's of the motor get high. Then the power comes on like gangbusters. Applications include high performance street use and racing where large volumes of air and fuel are required at high RPMs. Square port heads came with larger 2.19" intake and 1.88" exhaust valves. Some early closed chamber heads had 1.84" or 1.72" exhaust valves. Open or closed chambers were available with soft or hard valve seats. Once again, the open chamber designs on production heads will flow more air than the closed chamber production variety. If your engine is going to operate in the 7,000+ RPM range or if you are building a large cubic inch race motor, then the rec. port heads will make the power you need, but at a higher RPM."

Engine Mechanical / Electrical / Engine Harness Diagram Revised
« on: January 28, 2008, 06:12:38 AM »
I spent last night drawing up a color coded diagram of my engine harness. I hope it sheds some light as to how the engine side should be wired on a typical jet boat. Granted I run a full MSD setup and a 1 wire alternator, but it should give you somewhat of an idea on how to wire the motor.

WarZone / Well...
« on: December 29, 2007, 01:09:11 PM »
...I guess this will be my new home as well. Thought RDP would be a cool place to hang...unfortunately most of the people from Hot Boat ended up there. Talk about people who are quick to judge. One of them was a good friend of mine (or so I thought) and she decided to write me off over the mistake I made with the suction housing a month or so back.

Although I fixed the mistake, I see some people are not quite as forgiving as I am with people. Either that or they just thrive off of keeping the drama alive and would rather sacrifice a good friendship to make themselves look cool by creating drama over it. I guess some people either don't know the meaning of "bury the hatchet" or they just have more pride than they can possibly swallow.

Some people...

Engine Mechanical / Electrical / Jet Boat Engine Harness Diagrams
« on: December 28, 2007, 06:13:27 PM »
Here are 4 different engine harness diagrams, complete with wire gauge and colors.

Two of them show points ignition w/1 wire and 3 wire alternators.

The other two show HEI ignition w/1 wire and 3 wire alternators.

If you're using an aftermarket ignition such as an MSD, be sure and follow their instructions for wiring the box to the distributor.

If you're using an MSD R2R distributor by itself:
Black = Ground
Red = Ignition Hot & (+) terminal of coil
Orange = Tach Signal & (-) terminal of coil
No ballast resistor required

Engine Mechanical / Electrical / Auxiliary Solenoids
« on: December 28, 2007, 11:34:34 AM »
I'm sure most of you have seen some engines/boats use an auxiliary solenoid to run the starter, but what exactly does it do? What's the purpose of it? In this article I will explain exactly what the solenoid does and why we use them.

A solenoid is nothing more than a high current relay. A relay is nothing more than a switch, but instead of being actuated by a mechanical lever like an ordinary switch, it is actuated by an electromagnetic coil. When voltage is applied to the coil, the coil becomes an electromagnet. This magnet pulls the moving contact of the switch (normally referred to as the "common" contact) down to make contact with a second stationary contact, which completes the circuit it is connected to so that the circuit can receive positive voltage, thus turning it on. When the voltage is removed from the coil, it no longer is magnetic, so it cannot pull on the switch. Thus, a spring pushes the switch open, turning off the circuit that it is connected to.

The switch is in no way connected to the internal coil, so in order for the switch to work, a voltage source has to be connected to one of the switch's terminals. It does not matter which terminal of the switch it is connected to, just as long as it is connected to one of the switch's terminals. This terminal of the switch becomes the "line" side. The device to be switched on and off gets connected to the other terminal of the switch, and this side becomes the "load" side of the switch. The other side of the device gets connected to ground.

One terminal of the coil gets connected to ground. It does not matter which terminal of it goes to ground, just as long as one of the coil's terminals gets connected to ground. The other terminal of the coil goes to a mechanical switch, and the other terminal of this switch goes to an external voltage source, being the (+) terminal of the battery.

Switches are not polarized/non-directional...meaning that it doesn't matter which terminal of the switch goes to the "line" and which goes to the "load".

On a solenoid you have a total of 4 terminals: 2 big terminals and 2 smaller terminals. Refer to figure 1 below.

The two bigger terminals are the switch and the two smaller terminals are the coil. When you apply 12 volts to the smaller terminals, there will be a complete circuit (more commonly referred to as "continuity") between the two bigger terminals. You will also hear a 'click' sound as the switch closes.

When you take the 12 volts off of the two smaller terminals, you will have a broken circuit (more commonly referred to as "no continuity") between the two bigger terminals. You will also hear a 'click' sound as the switch opens.

What a solenoid is used for is to turn the starter on and off. The bendix on the starter is also a high current relay and the solenoid is used to switch the bendix/relay coil on the starter on and off. Figure 2 below shows a typical starter circuit with an aux solenoid.

Voltage to the starter is pulled directly from the battery. When voltage is applied to the "S" terminal of the starter, a contact in the bendix closes to a second large terminal on the back of the bendix that the starter motor is connected to, allowing the starter to turn on. The aux solenoid is what turns this "S terminal voltage" on and off. When you turn the key switch to the start position, the "BAT" terminal of the key switch contacts the "SOL" terminal of the key switch, which sends voltage to the coil in the aux solenoid, thus turning it into an electromagnet. The electromagnetic coil pulls the switch in the solenoid closed, which connects the + terminal of the battery to the "S" terminal on the starter bendix.

Now you're probably wondering "Why are we using a switch to control a switch that controls a switch?"'s why.

You could use the key switch to control the starter motor's "S" terminal directly. However, there will be a lot of arcing in the key switch everytime you turn it to Start due to the high current draw of the starter bendix. On top of that, the current would have to travel down 15' - 20' of wire just to get to the key switch, then another 15' - 20' back from the switch to the starter. That's 30' - 40' of wire total that the current must flow through. The longer the wire run, the more resistance the current encounters, which causes a voltage drop to the starter's "S" terminal. An aux solenoid can function with a voltage as low as 9 volts, however a starter bendix cannot. By using the solenoid and locating it close to the engine, the "S terminal current" has a lot less distance to travel from the battery to the "S" terminal (no more than 5' total). On top of this, you usually use a super heavy gauge battery cable to feed the line side of the aux solenoid's switch, which can more than handle the current drawn by the starter bendix coil with almost no voltage drop in between. Since an aux solenoid coil draws a lot less current than the bendix coil, this eliminates the 'arcing' in the key switch, thus making it last longer.

Another benefit to using an aux solenoid is that you can use the line side of the solenoid's internal switch (the larger terminal of the solenoid that the (+) side of the battery connects to) as a master terminal to connect everything that receives power all the time regardless of key switch position. You can also connect the charge wire of the alternator to this terminal as well.

Engine Mechanical / Electrical / Marine Electrical Standard Color Code
« on: December 28, 2007, 10:48:36 AM »
As a wiring technician/enthusiast, I have always been a stickler of sticking to the color code of whatever I'm wiring. Some guys don't really care about the color code...they just want the damn thing to work. However, I prefer the color code for a few reasons:

1) The wiring job looks like a professional did it
2) Easier troubleshooting for you
3) When you go to sell the boat, everything is done to a standard to allow the new owner to troubleshoot easier

So here I will post the marine standard electrical color code for jet boats:

Black - All grounds
Red - Constant hot (all wires that have 12 volts on them regardless of key switch position, "BAT" terminal on key switch)
Purple - Hot In Run (switched hot, controlled by key switch i.e. ignition, gauges, etc, "IGN" terminal on key switch)
White - Hot In Start (runs the starter bendix or aux solenoid)
Light Blue - Oil Pressure Sender; "S" terminal on Oil Pressure gauge
Light Brown or Tan - Water Temperature Sender; "S" terminal on Water Temperature gauge
Grey - Tachometer signal from ignition; "S" terminal on Tachometer
Orange - Bilge Pump hot from switch to pump
Pink - Bilge Blower hot from switch to blower
White/Red - Fuel level sender; "S" terminal on Fuel Level gauge
Yellow - Lights from switch to lights

Projects / Pump Is Back Apart...
« on: December 27, 2007, 10:27:52 AM »

However this time it's not due to a problem. I'm doing a split bowl/droop conversion...swapping from the C bowl to an American Turbine split bowl w/droop.

Just got the pump off of the boat yesterday...and I found the source of my water leak. Somehow when Beerjet and I reinstalled the pump a washer got stuck between the transom housing gasket and the transom. So hopefully my leak will be gone when I get the pump back on.

Engine Mechanical / Electrical / Terminal Blocks Explained
« on: December 26, 2007, 08:08:52 AM »
Ever wonder why your engine on your boat has a terminal block?  More commonly called the "barrier strip", its purpose is to provide a disconnection point between the engine wiring and the dash wiring. This is so that you can leave the engine wiring intact and easily disconnect the dash wiring in the event that the engine needs to be pulled out, saving time and headaches.

I have attached two diagrams of how a barrier strip is typically wired. Some boats use a 7 position strip while others use an 8 position strip. The only difference being that the 8 position strip allows a connection for the alternator's "Charge" wire, but quite honestly I see no reason for the alternator to be connected to the strip since it does not run to the dash, so a 7 position strip is perfect if you're replacing your wiring or wiring up a brand new boat.

Of course...this is the way it has been done since the first jet boat was created. A more modern way of doing it is by using a 7 pin weatherpack connector. It's much quicker to disconnect than having to unscrew 7 wires from a barrier strip, and it keeps your connections sealed from the elements unlike a barrier strip. Weatherpack makes 'pigtails', which are the connector with wires already crimped internally that you spliced into your existing wiring. If you know how to solder and heat shrink, I recommend going this route so you wont have to buy any special crimp tools to assemble the connector. The pigtails come in 1, 2, 3 and 4 pin style. You can use a 4 way and a 3 way connector to connect all 7 wires. If the alternator originally connected to the barrier strip, I would just run an 8AWG wire from the charge terminal to the battery + terminal to correct this.

In the diagrams you will see that one side of the strip is the "Engine" side while the other side of the strip is the "Dash" side. These diagrams show what wire is what from left to right as you're looking at the back side of the engine while standing behind the transom.

7 Terminal Block
Engine Side:

Terminal 1 (ground): This wire is a short wire that runs to the engine block. The negative terminal of the battery connects to the block, so by running a wire from this terminal to a bolt on the engine block will connect this terminal to the negative side of the battery.

Terminal 2 (battery +): The wire from this terminal can be connected to one of 3 places. You can either run it straight to the battery's + terminal, or the battery + terminal on the starter, or if you're running an aux solenoid you can run it to the terminal on the solenoid that connects to the + terminal of the battery. I run an aux solenoid so this is the way I have mine set up.

Terminal 3 ("S" terminal on starter): This terminal runs directly to the terminal labeled "S" on the back of the starter bendix, or to the coil on the aux solenoid. When running an aux solenoid, the "S" terminal of the starter will receive power directly from the battery when the aux solenoid is switched on by this wire.

Terminal 4 (Ignition + voltage source): This wire depends on the ignition system you're running. Basically this terminal only has power on it when the ignition switch is in the "On" or "Run" position. We call this the "Hot In Run" terminal. I have listed a few of the common ignitions to give you an idea:
HEI: Goes to the BAT+ Terminal on distributor
Points Ignition: Ballast resistor which connects to the + terminal of ignition coil
MSD R2R Distributor (no box): Red wire on distributor
MSD Box: Red wire on 6 pin weatherpack connector

Terminal 5 (oil pressure sending unit): This terminal connects to the screw terminal on the top of the oil pressure sending unit.

Terminal 6 (water temperature sending unit): This terminal connects to the screw terminal on the top of the water temperature sending unit

Terminal 7 (tachometer signal from ignition): This wire depends on what ignition you're running. I have listed a few to give you an idea:
HEI: Runs to the "Tach" terminal on the distributor cap
Points type ignition: Runs to (-) terminal of the ignition coil
MSD R2R Distributor (no box): To (-) terminal of the ignition coil
MSD Box: The box will have a seperate wire for the tach signal...that wire runs to terminal 7. You may need a tach signal adapter, which MSD supplies, depending on what brand of tach you're running. Check MSD manual for your particular ignition for more information

Dash Side:

Terminal 1 (dash ground): This terminal connects to a master ground wire, preferrably of a heavier gauge (10AWG or bigger). This wire will be the master ground feed to all the dash mounted accessories.

Terminal 2 ("BAT" terminal of ignition switch): This terminal connects straight to the "BAT" terminal of the ignition switch and should be of heavy gauge (10AWG or bigger). This wire is the master power feed for all dash mounted accessories. This wire is constantly hot at all times. Any circuits that will receive power regardless of ignition switch position will be powered from this wire (i.e. bilge pump circuit).

Terminal 3 ("SOL" terminal of ignition switch): This terminal connects straight to the "SOL" terminal of the ignition switch. This wire only receives power from the "BAT" terminal of the switch when the key is in the "Start" position. This wire feeds power back to the starter bendix or solenoid to tell the starter to turn on.

Terminal 4 ("IGN" terminal of ignition switch): This terminal connects straight to the "IGN" terminal of the ignition switch. This wire receives power from the "BAT" terminal when the key is in the "On" or "Run" position. This wire supplies power to the ignition system (or an "On" signal to MSD box ignitions). Also, any circuits that receive power only when the key is on will be powered from the "IGN" terminal of the switch (i.e. gauge circuit).

Terminal 5 ("S" terminal on oil pressure gauge): This terminal runs to the "S" terminal on the back of the oil pressure gauge to connect it to the oil pressure sending unit

Terminal 6 ("S" terminal on water temperature gauge): This terminal runs to the "S" terminal on the back of the water temperature gauge to connect it to the water temperature sending unit

Terminal 7 ("S" terminal on Tachometer): This terminal runs to the "S" terminal on the back of the tachometer to connect it to the tach signal from the ignition

Engine Mechanical / Electrical / Ignition Systems...How Do They Work?
« on: December 25, 2007, 08:24:07 PM »
We all know what an ignition system does, but how does it do it? In this article I will explain the basic operation of the two different types of ignition systems: inductive and capacitive discharge (commonly called CD ignitions).

An inductive ignition is comprised of a coil, distributor, and either breaker points or a magnetic pickup type trigger. The inductive igntion receives its power directly from the battery and stores all of its spark energy within the coil.

The ignition key switch typically has 3 terminals on it. They are labeled "BAT", "IGN" and "SOL". "SOL" powers the starting circuit while "IGN" powers the ignition and everything else with "switched power" (i.e. circuits that only receive power when the key is turned to the "On" position, such as the gauges). The "BAT" terminal gets connected to a +12 volt source. This terminal is the moving contact of the switch that makes contact with the "IGN" terminal in the "On" position, and both the "IGN" and "SOL" terminals in the "Start" position.

In the "Start" position, both the "SOL" and "IGN" terminals receive +12 volt power from the "BAT" terminal of the switch. This is so that while the starter motor is spinning, the ignition can receive power in order to fire the engine during starting. When the key is released from the "Start" position back to the "On" position, power is removed from the "SOL" terminal and only the "IGN" terminal receives power from the "BAT" terminal. This turns off the starter, but leaves the ignition on to keep the engine running.

On a points type ignition, the "IGN" terminal runs to a ballast resistor near the ignition coil. The other side of the ballast resistor connects to the + terminal of the ignition coil. The purpose of the ballast resistor is to limit the voltage to the coil so that the coil does not overheat. The (-) terminal of the coil gets connected to the breaker points inside of the distributor. The other side of the breaker points gets connected to ground.

The ignition coil is nothing more than a step up transformer. It takes 12 volts from the battery and steps it up to about 15,000 volts to run the spark plugs. The transformer is comprised of two coils: the primary coil and the secondary coil. The + and - terminals are the primary coil while the center contact of the coil is the secondary coil. The other side of the secondary coil is internally connected to the - terminal of the coil.

When voltage is applied to the primary coil, a magnetic field builds up around the primary coil. The secondary coil passes right through this magnetic field, but is not phased by it. When power is taken away from the primary coil, it causes the magnetic field to collapse. It also generates about a 250 volt spike . This generates a "counter voltage" in the secondary coil that is much higher than the spike voltage, but much lower in current. This is because the secondary coil has much more turns of wire than the primary coil. The turns ratio between the primary and secondary coils is typically around 100:1 (1200 turns of wire in the secondary for every 1 turn of wire in the primary). With this ratio, a primary spike voltage of 250 volts will induce a counter voltage of 25,000 volts (250 volts x 100= 25,000 volts).

In order for a voltage to be induced into the secondary coil, current flow through the primary coil must be interrupted momentarily to cause the magnetic field around the primary to collapse. This is the function of the trigger circuit, which on a points type ignition it is comprised of a set of breaker points. The breaker points are nothing more than a switch that is opened and closed by a cam that rotates inside of the distributor. The breaker points are connected between the - terminal of the coil and ground...they provide a ground path for the - terminal of the coil. When the cam passes over the breaker points, the contacts seperate, which interrupt the ground path to the - side of the coil, which interrupts current flow through the primary side of the coil. This causes the magnetic field around the primary to collapse, inducing the counter voltage into the secondary coil. This voltages gets sent to the rotor contact inside the distributor, which routes the high voltage to the correct spark plug.

Something else the breaker points do is send a trigger signal to the tachometer to tell the tach how fast the engine is spinning. By counting the pulses created by the points opening and closing (the points open and close faster as the engine spins faster), the tach can display how fast the engine is spinning.

On an electronic ignition, the points are replaced by a magnetic pickup. The magnetic pickup provides a ground. Everytime the non magnetic trigger wheel passes through the magnetic pickup, it interrupts the ground to the coil, causing the primary's magnetic field to collapse, which induces the higher voltage into the secondary coil. Electronic ignitions do not use a ballast resistor.

An HEI ignition is probably the simplest ignition to wire. You only have 2 terminals on an HEI distributor: + Power and Tach. The "IGN" terminal of the ignition switch supplies power to the + Power terminal while the Tach terminal gets connected to the "sense" terminal on the tach. All ground connections are internally connected to the distributor housing and receive their ground from the engine block since the negative terminal of the battery is connected to the block.

One of the major disadvantages to an inductive ignition is that all of the spark energy is stored within the coil. Because of this, the engine can reach a certain RPM where the coil doesn't have enough dwell time to recharge itself before the next cylinder is fired. Exactly where this RPM point will be depends upon the type of ignition system used and the specific characteristics of the engine in question. When this RPM point is reached, there is insufficient initial spark energy to jump the spark gap and ionize the air/fuel mixture, and the coil will be unable to fire that cylinder, generating a miss. If you increase RPM further, additional misses will be generated and eventually the ignition system will be unable to fire any combustion chamber. This is called "crash," and engine performance hits a wall.

This is where CD ignitions come in. CD stands for "Capacitive Discharge" and relies on the discharging of a capacitor to power the ignition coil.

On a CD ignition, all of the spark energy is stored within a capacitor. A capacitor within the ignition box stores a voltage of around 460 - 480 volts. A capacitor can recharge a lot faster than a typical ignition coil can, and under ideal conditions can receive its full charge without rolloff up to 15,000 RPMs or so.

We'll use an MSD ignition as our example for the operation of a typical CD ignition system.

On a typical CD ignition, you have a coil and a distributor just like an inductive type ignition, however you also have a box called an Ignition Pulse Amplifier. This box pulls power directly from the battery and has a seperate "turn on" circuit internal to the box that receives 12 volts from the "IGN" terminal of the ignition switch to tell it when to turn on or off.

Inside the box you have a step up transformer. This transformer steps 12 volts from the battery up to around 460 - 480 volts. This transformer charges a capacitor inside of the box. The capacitor discharges this voltage through the primary side of the ignition coil when the trigger circuit (typically a magnetic pickup trigger) tells it to. By sending a higher voltage into the primary of the ignition coil, the secondary coil voltage also increases.

With a turns ratio of 100:1, a discharge voltage of 460 - 480 volts will create a secondary voltage of 46000 - 48000 volts...much higher than that of a typical inductive ignition.

The other advantage to CD ignitions is multiple spark discharge. Up to 3000RPMs, the ignition delivers multiple sparks through 20* crankshaft rotation upon each firing of the ignition. Above 3000RPM the ignition cannot supply multiple sparks fast enough so it only supplies 1 spark above this RPM, but the spark duration remains at 20* at any RPM. Below 3000RPMs, the multiple spark feature reduces plug fouling at extended periods of idle such as in the no wake zone.

The following connection information is for an MSD 6M2 Marine ignition box:

There are a total of 7 connections on a typical MSD box. Two of these are the + and - connections to the battery. These wires are hardwired internal to the box and are seperate from the weatherpak connectors on the box. These wires are a heavy gauge red and black wire. These wires are the wires the ignition system draws power from. If you wish to fuse the red wire, the ignition draws 1 amp per 1000RPMs. Since most jet boat motors don't spin higher than 5000 - 5500RPM, I recommend the use of a 10 amp fuse.

The 6M2 box is to be used with the MSD Blaster or Blaster2 coil.

On the 6 pin weatherpak connector you have 6 wires, along with a single pin weatherpak connector which only has 1 wire. This one wire is your tach signal to go to the sense terminal on the tach. The 6 pin connector's connections are as follows:

Orange: + terminal of coil
Black: - terminal of coil


Red: Ignition "On" Signal...goes to the "IGN" terminal of the ignition switch

Green/Purple Connector: This connector is used for the MSD Pro Billet Distributor, or another distributor with a magnetic pickup. Green - +, Purple - (-)

White: This wire is used for a points type distributor or the MSD Ready To Run Distributor. On the R2R, this wire gets spliced onto the orange wire of the distributor

If you run the MSD box I highly recommend the use of the MSD Ready 2 Run distributor. This type of distributor has its own onboard ignition module and does not require the box, but will work with it. The reason behind using the R2R with the box is for redundancy. If the box fails, it can be easily bypassed and the ignition will work direct from the distributor. You won't get the super high voltage spark, but the ignition will work and the engine will run with some sacrafice in performance.

Interior / Carpeting
« on: December 25, 2007, 10:33:35 AM »
Hey guys....I'll be installing the carpet in my boat within the next couple of months and was just curious as to what the best type of adhesive would be to use on it.

Jet Pumps / Jet Boats...How Do They Work?
« on: December 22, 2007, 01:38:31 AM »
I see a lot of misconceptions regarding how jet boats work. Lots of guys have a misconception that they work just like prop boats, which work very similar to a car. Lots of guys apply the same tuning principles as they'd apply to a car to tune the engines just because it's an automotive engine, however the same rules do not apply. In this article I will explain the differences between cars, props, and jets and what their differences are in operation.

Before you go any further, this article explains the basic physics and concepts of jet boats assuming an ideal/perfect world. In actual operation, there are other variables which are not explained here that the pros can better fill you in on, but for simplicity this article will give you the basic understanding of the concept of jet boats/pumps and arm you with the knowledge to properly tune the engine to work with the kind of load a jet pump places on it.

In my first example, let's talk about what goes on with the engine and powertrain/drivetrain in a car. A car at a dead stop only allows the torque converter in the transmission to spin up to the converter's rated stall speed. Let's say you launch the car at wide open throttle (W.O.T.) and your torque converter stalls at 2000RPMs. The engine will only swing up to 2000RPMs until the car starts moving. Once it starts moving, the wheels start turning and "unload" the engine. The faster the wheels spin, the more the engine unloads, allowing the engine to pick up RPM and spin faster. The speed of the vehicle and the speed of the engine continue to climb...once the engine reaches the RPM that is near the end of the engine's power band (the range of RPM where the engine makes power), the transmission shifts to the next higher gear, which reloads the engine, dropping the RPM back down into the low side of the engine's power band. However, the car continues to pick up speed due to the higher gear ratio.

As the car picks up more speed in the next higher gear, again the engine unloads, picking up more RPM the more it unloads, until the transmission shifts to the next higher on and so forth. Transmission gear ratios, rear axle gear ratio, and circumference will determine the RPM/MPH relationship. This never changes...however, the weight of the vehicle will determine how much torque has to be made at that RPM to move the vehicle and keep it moving at a constant speed. The more weight you add, the more torque will need to be made to move the vehicle.

Typically when you select a cam for a car, you select a cam that matches the torque converter's stall speed. The stall speed allows the engine to swing up to the RPM where the engine starts to make big torque, then loads the engine at that RPM in such a way that causes the engine to make big enough torque to get the vehicle moving. Most car engines are set up to make big torque in the lower range of RPM...this keeps engine wear and fuel consumption minimal, since the engine doesn't have to spin as fast, requiring less fuel and exerting less strain on the engine.

Prop boats are very similar. A prop acts very similar to a torque converter and a tranny all in one. The prop size/blade pitch will control what the boat's max RPM will be at a dead stop...i.e. the "stall" speed, just like a torque converter. As the boat picks up forward speed, the front of the prop unloads, allowing the engine to pick up RPM as the boat speed increases, very similar to how turning wheels assist the engine in removing the load for a car motor to pick up RPM.

Jet boats...totally different animal. Jet boats work off of thrust, which is a perfect example of Newton's 3rd Law: "For every action there is an equal and opposite reaction". Jet pumps pump water into a bowl, where it is pressurized into a bowl and leaves the pump outlet at a high rate of speed. This creates a backward moving thrust, which pushes the boat forward. Think of a fill it up with air and let it go. The balloon flys across the room. The air is exiting the balloon in a direction opposite of the balloon's flight direction, thus creating your equal and opposite reaction.

The weight of the boat and the amount of thrust the pump is capable of generating determine's the thrust/weight ratio. The weight of the boat along with the hydrodynamic design of the hull will determine how much thrust will be needed to move the boat at a certain speed. The impeller size ultimately controls how much thrust is generated at a given RPM (there are other factors as well that control this, but for simplicity we'll get into that later). The impeller size also governs how much horsepower is needed to spin it to a given RPM. The faster you spin the impeller, the more horsepower will be absorbed. Different size impellers have different horsepower requirements. For example, we'll use Berkeley brand impellers since they seem to be the most common.

Berkeley impellers are identified with letters: AA, A, B, C, so on and so forth. The higher the letter, the smaller the impeller size and the less it loads the engine, which means the less horsepower required to spin it to max RPM. In other words, it takes less horsepower to spin a C impeller to 5500RPM than it does an A impeller.

However, an A impeller spun to 5500RPM will generate more thrust than a C impeller spun to 5500RPM, but will require more horsepower than the C impeller will to spin it 5500RPM.

Take a look at figure 1 below. This is the Berkeley Impeller Power Curve chart, which will show you how much horsepower is required to spin the different impeller sizes at a given RPM.

Looking at the chart, you can see that 400hp is required at 5050RPM to spin an A impeller to 5050RPM, but only 280hp is required at 5050RPM to spin a C impeller the same speed. However, the A impeller at 5050RPM will be generating more thrust than the C impeller will at 5050RPM because more water is being moved by the A impeller at that speed. The more water the impeller moves at a given RPM, the more of a load the engine will see, and the more horsepower you will need to spin it up to that speed. However, since it moves more water at that speed than a C impeller, it creates more water pressure in the pump, which means more thrust generated at that RPM.

Now we'll get into the how the engine operation differs from how it operates in a car.

In order to generate large amounts of thrust, the pump needs to be spun a lot faster than the drive train in a car. Below about 3000RPMs, the pump doesn't provide much of a load for the engine to make any kind of torque...therefore not much thrust is generated. Thrust is generated not only by how fast the pump is spinning, but also how hard it is being spun. Once the pump reaches the RPM at which it 'hooks up', it's starting to move a lot more water, which loads the engine accordingly, necessitating the need for the engine to make big torque at the RPM where the pump really loads up. This usually happens at about 3000-3500RPM. For this reason, most jet boat engines are tuned/cam'med to make big torque throughout the 3,000 - 5500RPM range. As the pump RPM increases, the amount of water the pump is moving also increases, which loads the engine more and more, causing the torque/horsepower demand to also increase.

At some point, the impeller's horsepower curve will cross the engine's hp curve on the downside of it. The RPM at which the two curves meet on the downside will be the max RPM the engine will be able to spin that particular impeller. At this RPM, the impeller's HP demand is still going up, while the engine's hp curve is going down. Because the engine can no longer make anymore hp, the engine is incapable of spinning the impeller any faster than this RPM.

The engine is capable of spinning a jet pump as fast as the pump will allow it to regardless of whether or not the boat is moving or how fast or slow the boat is moving through the water. Boat movement has no effect whatsoever on the load that the engine sees from the pump. The pump and the engine have no idea that they're even moving anything. As far as the pump is concerned, it could care less if it were mounted to a boat or a stationary platform...all it does and ever will do is pump water. For this reason, pump RPM is completely unaffected by the weight of the boat or by the boat's forward speed. The impeller cut, tightness of the pump tolerances, nozzle size, etc etc...will determine how much thrust is generated at what RPM and how much of a load the engine will see at given RPMs. The max available RPM is determined by what impeller you're running and how much horsepower the engine makes at what RPM.

The advantage of being able to spin the pump at 100% RPM from a dead stop is that you achieve 100% thrust immediately, which makes the boat a lot more responsive than a prop. Quicker holeshot and more responsive turning are a couple of things that result from this.

Think of the pump as a high stall torque converter. According to our impeller chart, if we had a 500hp engine built to exactly match the curve of an A impeller, your max RPM would be 5400RPM. This means that our "torque converter" would stall at 5400RPM and would not allow the engine to spin any higher than that. However, since max RPM is unaffected by the boat's forward speed, you could have the boat at a dead stop or running balls out at WOT, and the pump will only allow the engine to spin up to 5400RPM. The weight of the boat, passengers and cargo and design of the hull would determine what the boat's max MPH will be.

You could also think of the pump as you would a jet engine. Jet engines have N1 and N2 RPM...N1 is the first stage fan and N2 is the second stage fan. The RPMs of N1 and N2 are expressed as a percentage (ex. 50% N1RPM or N2 RPM). Regardless of forward speed of the jet aircraft, 100% RPM=100% can go no higher (with the exception of having afterburner on a jet aircraft). And just like a jet pump, a jet aircraft engine's RPM has nothing to do with the forward speed of the aircraft, but everything to do with the amount of thrust generated (more RPM=more generated thrust). And just like a jet boat, a jet aircraft's weight and design will control max available speed, depending on how many bombs and munitions are loaded (not only the total munitions weight, but the added drag imposed by the loaded munitions also plays a part in max available forward speed). The only difference being that a jet pump only has 1 stage and it's an impeller, not a fan, you could say 5400RPM = 100% RPM. If your max RPM=5400 and you cruise at 3700-3800RPM, you're cruising at 70% RPM.

Another thing you'll notice as you drive a jet boat is that it takes time for the boat speed to 'catch up' to the RPM. Unlike a car who's RPM increases with vehicle speed (due to the unloading of the drivetrain), when you accelerate a jet boat, it immediately swings up to 'X'% RPM (depending on how much throttle you give it) and stays there while the speed of the boat increases. Once the boat reaches the speed at which the amount of thrust applied = momentum, the boat stops accelerating and maintains that speed until you either add or subtract the amount of thrust applied by increasing or decreasing RPM. This action supports the fact that engine/pump RPM and boat speed are not related to each other in any way.

Knowing how this type of a load works an engine should help you to determine how to properly tune the engine to work with this kind of a load on it in regards to timing and fuel curve.

The No Wake Zone / So who fell victim...
« on: December 18, 2007, 03:52:37 PM » Hot Boat's recent mass member ban?

Engine Mechanical / Electrical / Engine Cooling
« on: December 12, 2007, 10:57:22 AM »
How are you guys running the water plumbing on your boats? What are your running/idle temps?

Here's mine as follows:

                                   Garden Hose Fitting
                                       Ball Valve                              Overboard Dump
                                              |                                             |                             -------> Drvr side water inlet
                                              |                                             |                            |
Pump --> 1/2" ball valve --> T Fitting --> T Fitting --> Water Bypass Regulator               |
                                                             |                                                           T
                                                             |                                                           F
                                                             |                                                           i
                                                              --->5/8" heater hose -------------------> t
                                                                                                                         ----------> Pass side water inlet

Hardin Marine thermostat kit with two 5/8" overboard dump lines.

Header water is fed off the intake manifold crossover, to a gate valve, to the Bassett T valve, to the header water injection lines.

With a 160* thermostat, my engine runs a bit too cold (less than 140*) I like to see 160 - 180. I know most people think "the colder the better", however from what I know hotter temps yield better performance and fuel economy. I did find out that the pressure regulator was coming on too early, which we've readjusted it to 12psi with air...gonna have to run it to see where I'm at with it since we fixed that.


Jet Pumps / Is anyone here...
« on: November 23, 2007, 11:03:37 AM »
...running Hi Tech Performance's Ultimate Wear Ring? Pros? Cons? What did it improve?

Engine Mechanical / Electrical / Banderlog Substitution
« on: November 20, 2007, 12:15:24 PM »
So I thought about getting the Banderlog valve...

However, someone clued me into an idea that would be way cheaper to do. Out of curiosity, has anyone thought of getting an MSD RPM Activated switch and a solenoid valve? The RPM switch would run about $70, while the solenoid valve would run another $50-$60. For a total of $130-$140, you could have the ultimate in header water control.

Install a 2000 RPM pill into the RPM switch and you're good to go!

I'd like to hear everyones' opinions on this alternative.

The No Wake Zone / Cabin Fever...
« on: November 18, 2007, 09:17:16 PM »
fukkin sucks ass!!! Is it summer yet!? :D

OK so we're in for a long winter...from the feel of it I'm thinkin' it may be another dry winter (perhaps worse than last's still 75* here!!!)....however I know we all have the list of winter add-ons/projects goin', so let's post 'em here. I'll start.

Your mom (yes I named my boat Your Mom) is officially in drydock. Propless and I pulled the motor out last weekend, and there's quite a bit to be done before it goes back in.

I've removed the Jet-A-Way from my pump...yes it's an awesome piece and does everything it says it does...and I'm gonna miss the "neutral" feature...however, I need more back seat space and my motor is sitting too far forward, which we think is messing up the CG of the boat, causing it to run too wet. So that will set the motor back another 4-5". Also, for some reason my U-Joint shaft had a little play on the end of the Jet-A-Way shaft, but has absolutely no play on the pump shaft itself. I had noticed a bit of vibration before...I'm hoping this solves that problem as well.

Tom at JBP is buying it off of me, and I'll be getting an AT split bowl w/droop and a Berkeley front bearing cap (to replace the Jet-A-Way). Also I'm thinkin' of changing my handhole cleanout swingbolts over to the billet ones Tom recommended to me awhile back to keep the cover from coming off in the event of shock loading the pump.

Hopefully before the summer hits I can send the boat to him and have him machine my intake for a shoe/ride plate, and also I'll be installing a loader as well.

As far as the engine goes, I had a fuel leak from when I first got the motor running, which stained my intake manifold (don't ever buy the el cheapo dual fuel feeds from Pep Boys..they suck!!!). I've since replaced it with a Holley dual feed line, which fixed the leak, but the intake is off and will be going to the powder coat shop next week, where they'll bead blast it and powder coat it to make her look new again. I'll also be getting a new set of valve covers for her too. Maybe throw on a second coat of paint to clean the motor up a bit.

Also...I never got a chance to carpet the boat before I ran her a few times, so the seats/tanks will be coming out and the same guy who upholstered my seats will be doing the carpet as well.

I'm also thinking of hardlining my cooling system like Beerjet did on his...Omar I'll be asking a few questions about how to go about doing that as well.

And last but not least, I'll be definitely neatening up the wiring on this bitch too.

All before next Memorial Day weekend.

Let's hear everyone's winter mod projects.

Winter mods=the cure for cabin fever! :D

Engine Mechanical / Electrical / Holley Carb Tuning Debate
« on: November 05, 2007, 08:38:33 AM »
So I've been hangin' with Propless lately and him and I have been really analyzing Holley carburetors and the need for a power valve.

It got those wheels turning in my brain. As I'm thinkin' about things, I start realizing the type of load that different vehicles/vessels place on a marine built automotive engine.

Lots of jet guys try to apply their automotive knowledge to a jet boat to tune them. Some of them end up chasing their tail...always tuning at the lake...they can never seem to get it quite right.

So the question a power valve really needed in a jet boat?

Before that question is answered, let's look at the type of load placed on the engine.

A car...from a dead stop places a certain load on the engine. As the vehicle picks up speed, the load on the engine decreases, allowing the motor to pick up RPM as the load on the engine drops. At a certain RPM, the transmission shifts to the next taller gear, reloading the engine, allowing the vehicle to pick up more speed, and unloading the engine again. This continues until the transmission locks up and becomes a 1:1 drive straight to the pumpkin. Your differential gear ratio will determine how many turns of the engine/drivetrain it takes to produce 1 turn of the wheel.

A prop boat...from a dead stop places a certain load on the engine. As the boat picks up speed, the front of the prop unloads, allowing the motor to pick up RPM as the load on the engine drops.

To summarize...a car/prop boat is a load that decreases with vehicle/vessel speed and is independant of RPM.

Now let's look at a jet. A jet is a constant load. From a dead stop, you hammer down to WOT and immediately go to max RPM. This max RPM is dependant on the size impeller and how much HP the motor is capable of making. The load placed on the motor is completely independant of the vessel's forward can tie the boat to a dock and still get your max RPM at WOT. However, the load placed on the engine increases with RPM...the faster you spin the pump, the more water you move through it, and the more it loads the engine.

Now back to the power valve...the reason for this debate is that we're trying to see if we can keep the power valve from opening and just dumping raw fuel through the motor when that extra fuel is not needed. Why burn more gas if you really don't need to?

Now my way of thinking is that on a jet, you would only need the power valve once you hit a certain RPM. At a certain RPM, a certain constant load will be placed on the engine that will cause the vacuum to drop to a certain point where more fuel than what the jets can supply is would need the power valve to open at that point. The power valve would remain open as long as the engine RPM is held above the RPM at which the power valve opens at. The reason for this is that load increases with engine RPM...which causes vacuum to drop even further...keeping the power valve open until you fall below the RPM at which the power valve opens.

Knowing would make sense to find out first at what RPM the stock power valve opens at. On a stock Holley 750DP 4150 carb, the stock power valve is a 6.5Hg. I would then use a vacuum gauge to find out at what RPM the motor drops to 6.5Hg of vacuum to find the RPM that the power valve opens at. I would then want to check my mixture at that RPM...if it's too rich I would want to change to a power valve that opens at a lower vacuum setting.

What are your thoughts? Am I correct in my way of thinking of how the power valve works in a jet?

Boat Showcase / Wheelie Shot
« on: October 25, 2007, 07:11:57 AM »
Took the boat out yesterday...I'm thinkin' I'm gonna need a split bowl w/droop and wedge to not only get my roost up higher, but so I can do better wheelies than this.

Was thinkin' of putting a 150HP shot of NOS on my jet boat. Anyone here ever driven a jet with NOS? What happens when you kick it in (as far as what does the boat do/how does it handle)? Is it like 'slammed in the back of your seat' response?

Engines / Engine Parts For Sale / 455 Olds For Sale
« on: January 10, 2007, 12:44:20 PM »
455 Olds pre-assembled long block...decided to go with a BBC.

Motor specs:

L2390F TRW Pistons
Stock Rods/Crank
Punched .030 over
"J" Heads modified with larger intake valves
W-30 Spec Cam:
.244/244 (Int/Exh) .050 duration
.475 Valve Lift w/1.6 Rocker Ratio
Roller Tip Rockers w/adjustable pre-load
Double Roller Chain
Melling F22HV High Volume Oil Pump
Restricted Cam Bearings
Restricted Push Rods
Hardin Marine 10qt oil pan
Brass freeze plugs

Asking $2500 obo

Call if interested.

Home: (559)292-6274
Cell: (559)994-6488


Random Boat Parts For Sale / 18' Trailer For Sale
« on: January 10, 2007, 12:42:13 PM »
18' Vanson single axle trailer for sale. Needs work. Must go Asking $500 obo.

Home: (559)292-6274
Cell: (559)994-6488


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