SoCal Jet Boats
Tech Talk => Jet Pumps => Topic started by: JBASHAM on August 28, 2015, 12:53:01 PM
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Got a hold of a different style loader and was wondering if this would benefit my boat or not?
Pro and cons?
18ft Bahner 454 12jg approx 450 hp boat does mid 70s.
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Current set up spins an A to 5000rpm no Diverter or droop.
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It will load your pump better and most likely drop rpm with that loader
Sent from McIntyre park
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What kind of boat and what power? One test is worth a thousand theories. Let us know what you find.
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It will load your pump better and most likely drop rpm with that loader
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So dropping RPM id most likely loose MPH correct??
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What kind of boat and what power? One test is worth a thousand theories. Let us know what you find.
Its a fairly light layup 82 18ft Bahner Bubbledeck. Mild 454 bored to 461, oval port heads, smaller cam, Victor Jr with a 750 DP, MSD HEI, OT Bassets. Approx 450 HP Spins an A impeller about 5000rpm. Mid 70s
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The long loader might make it feel "stuck to the water" if the ramps hang down too far. But since you don't have a shoe, a more aggressive loader might help load the pump harder. Unless you are currently unloading the pump, I don't think you would see a difference in RPM.
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The long loader might make it feel "stuck to the water" if the ramps hang down too far. But since you don't have a shoe, a more aggressive loader might help load the pump harder. Unless you are currently unloading the pump, I don't think you would see a difference in RPM.
My southwind 18 lost 200 RPM with that exact loader. B impeller no shoe or rideplate and 550hp.
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My southwind 18 lost 200 RPM with that exact loader. B impeller no shoe or rideplate and 550hp.
Compared to?
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Compared to?
My old boat had a Very similar set up to his.
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Jake, did you have a loader in it before going to the ramp style loader?
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Jake, did you have a loader in it before going to the ramp style loader?
Me? Or other Jake?
I looked on the Berkeley site and the one I have in now looks like the "SE" sport edition loader, and this new one looks like the SS loader.
I just wanna know if it'll hurt performance or not. Guess I should just try it then...
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So dropping RPM id most likely loose MPH correct??
This comment is incorrect.
On a jet boat, RPM has little to do with hull speed.
The determining factors are, in no specific order;
Hull weight, center of gravity, nozzle volume and velocity, drag coefficient.
RPM only indicates the relationship between the horsepower and the pumps ability to absorb it.
GT
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This comment is incorrect.
On a jet boat, RPM has little to do with hull speed.
The determining factors are, in no specific order;
Hull weight, center of gravity, nozzle volume and velocity, drag coefficient.
RPM only indicates the relationship between the horsepower and the pumps ability to absorb it.
GT
So if the pump is being loaded harder wouldn't it take more horsepower to sustain the same rpm? Therefore losing mph?
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So if the pump is being loaded harder wouldn't it take more horsepower to sustain the same rpm? Therefore losing mph?
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You're looking at it funny.
So lets say I can force some water into the pump with a very small increase in the drag effect.
Let's say that extra water provides the inlet of the impeller with a 30 psi NPSH (might want to look that up "Net Positive Suction Head" I'm a major nerd when it comes to this stuff.) That net pressure gain is a "freebie" and is work the impeller does not have to do. Now spin the impeller through it gaining a delta pressure of over 120psi..... That 150psi outlet pressure will be really valuable at the nozzle.
The reason the engine will be dogged down is because of the lack of cavitation, which "robs" the impeller of performance, or the ability to absorb power. Which can equate to added thrust. Ultimately that is the goal. Correct?
GT
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Correct?! You tell me! Lol! You know way more about this than I do.
I just want some opinions if this loader would be worth installing or not.
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The impeller should be the determining factor for RPM. Anything that deprives the pump of water will cause RPM to increase. Our current philosophy is to load the pump as hard as possible and cut the impeller to match the engine power curve.
Bowl pressure is directly influenced by suction pressure. Say your pump has the ability to step up the pressure 250 PSI. If you are loading your pump as hard as possible and you're developing 50 PSI on the suction side, bowl pressure will be 300 PSI. If you are only producing 10 PSI on the suction side, bowl pressure will only be 260 PSI.
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The impeller should be the determining factor for RPM. Anything that deprives the pump of water will cause RPM to increase. Our current philosophy is to load the pump as hard as possible and cut the impeller to match the engine power curve.
Bowl pressure is directly influenced by suction pressure. Say your pump has the ability to step up the pressure 250 PSI. If you are loading your pump as hard as possible and you're developing 50 PSI on the suction side, bowl pressure will be 300 PSI. If you are only producing 10 PSI on the suction side, bowl pressure will only be 260 PSI.
Isn't that what I just said? Hahaha
Yes, if installed properly and not set too deep, that loader is worth trying.
What do you have in it now?
GT
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Ok. I re-read your response.
So this loader should build more bowl pressure at a lower rpm because there will be less cavitation...correct?? More bowl pressure equals more mph regardless of the engine rpm?
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Isn't that what I just said? Hahaha
GT
To much multi-tasking makes me slow of the line
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Ok. I re-read your response.
So this loader should build more bowl pressure at a lower rpm because there will be less cavitation...correct?? More bowl pressure equals more mph regardless of the engine rpm?
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Theoretically yes. You're looking at it funny though.
It's difficult to use an absolute as far as the cavitation statement.
So lets just say if there is cavitation present, for sure. Providing the drag effect is kept in check.
GT
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To much multi-tasking makes me slow of the line
You taking a dump or clipping your toenails?
Lmao... I unfortunately know what your talking about.
GT
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Hahaha thanks a lot guys! I'll give it a try and report my findings.
GT, the loader in it now is a "SE" sport edition style loader.
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I unfortunately know what your talking about.
GT
Indeed you do!
Arguing with the wife while trying to buy bolts to mock up a fuel tank.
I much rather be talking about loaders on SCJB. I just need a job that will pay me to do that.
Cheers,
Joe
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Hahaha thanks a lot guys! I'll give it a try and report my findings.
GT, the loader in it now is a "SE" sport edition style loader.
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I think the Ass-O-Nom-Meter will be able to differentiate a performamce gain. It won't be huge, but betting you can tell.
GT
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Indeed you do!
Arguing with the wife while trying to buy bolts to mock up a fuel tank.
I much rather be talking about loaders on SCJB. I just need a job that will pay me to do that.
Cheers,
Joe
Your not being paid for your input?
Hmm. That's odd......
I'm expecting my monthly royalty check any day now. 8)
GT
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Your not being paid for your input?
Hmm. That's odd......
I'm expecting my monthly royalty check any day now. 8)
GT
I'm not yet vested
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I'm not yet vested
Get a couple more stars under your name and Brad will start cutting checks.
;D
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Get a couple more stars under your name and Brad will start cutting checks.
;D
LOL
A little shameless post whoring
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So...
this style of grate increases(helps) the pumps performance....at about the time the boat gets or is getting on plane all the way up max speed. would this statement be correct?
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So...
this style of grate increases(helps) the pumps performance....at about the time the boat gets or is getting on plane all the way up max speed. would this statement be correct?
Hmmmmm.
Have to answer it this way or it could effect my salary. :o
It really depends on how it's set up and what the pump requires.
I know that sounds like a cop out, but there is no silver bullet.
I have found that the loaders really don't do squat until the hull is freed up and on plane (sometimes called "taking a set", even though that's more of a vee drive term).
GT
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copy....
i was just curious where this mod helps the most. bottom, mid, top end....
similar deal on my stand up...makes it hook or stick to water better...particularly in some chop. overall speed?....i felt no difference. just that it would stay hook longer before unloading pump. so i guess in a race....id have more traction than someone without that grate. (take that last statement loosely)
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So...
this style of grate increases(helps) the pumps performance....at about the time the boat gets or is getting on plane all the way up max speed. would this statement be correct?
Ok I'm gonna give it a try. On my Gullwing I have tried two different loaders MPD vs B1. This is my conclusion after testing. Mpd loader without nos I would run 6400rpm without nos at 98 mph, with nos I ran a 106 but has a problem unloading, B1 loader boat will only do 96 on motor at 6200 and ran a best to date to 113 with absolutely no unloading problem. Conclusion is you need to pick the right loader for what your hp range is. If I were to race everyone on motor i choose mpd but I don't I set my boat up for nos and Chris did a awesome job with his loader and could not ask for more. So in my mind you can overload the pump and loose mph. Don't stick a big loader in your boat if you can't push the water.
"RTCP"
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Sorry... On the road for 3 hours. 👎👎 went from a ski rock grate to the SE bullshit type loader. Lost 200rpms
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Thanks, I'm not trying to take over thread...sorry if it seemed so...http://
I only ask to gauge similarities between pwc and jet boat applications. I fully understand the benefits or workings of a loader grate. I just wanted to see if there were similar or the same as it is on a pwc.
It's clear there are some differences ... for my pwc app....I was only concerned with "traction" if you will...top speed was irrelevant as I was not racing. Nor had something to prove.
The one thing I am puzzled with is the shut down or unloading part....
Some say X item had rougher shut down than the other...this is somethin new to me as I never experienced it on my stand up....or sitdown. Lol, or is it that I wasn't going fast enough? Haha. Anyhow...
Thank you all!
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Since this is loader talk, can I ask a newbie question? What is "unloading"?
I'm already planning to have B1 build me a loader but I need to see what mine will do as is with the angle iron thing that is in my intake right now.
Garrett
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Here's a crappy pic of what I'm working with. Sorry, not trying to hijack this post, just trying to learn.
Garrett
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I'm chewing on the popped corn with ya buddy....
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I think most of you have been in a jet boat in rough water and heard the rpm come up and lose forward thrust. The pump unloaded due to lack of incoming water This can also be a problem if flat water most of the times it will be on the higher hp boats. Setup becomes very important at this point. I'm know expert on this or any other subject ( disclaimer). When I revamped my boat I had a few issues with this unloading deal. Mine was only up river at about 80 mph but bad enough to drop a wing back in the water and make you pucker up. Temp fix remove 4 degrees of up nozzle and it stop the unloading. I'm headed to the correct perm fix now now I will be adding 125 thousandth of shoe add see where that goes. The boat still stops clean and straight if you side step at 90 mph. The B1 loader I'm using now is a great loader and not my problem the boat overall setup is the suspect. My boat simply airs it self out of the water no water to load. Thanks to Joe I have been cleaning the problem up. Hp problems they exist on both ends.
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Here's a crappy pic of what I'm working with. Sorry, not trying to hijack this post, just trying to learn.
Garrett
That looks like the SE loader. Same one I currently have in mine. I think it's one step up from a stock rock grate.
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"You are better off running nothing than you are running a rock grate" - Jack McClure.
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In fact, this is what we think of rock grates. We don't serve their kind here. They have to wait outside.
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In fact, this is what we think of rock grates. We don't serve their kind here. They have to wait outside.
hahaha joe!! 👍👍
"RTCP"
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In fact, this is what we think of rock grates. We don't serve their kind here. They have to wait outside.
In that case, I'll be seeing you on Monday.
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Have preloader,stuffer,aggressor 9,straight snoot, wedge,diverter,shoe/plate an I still run a rock grate. Runs very well
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Have preloader,stuffer,aggressor 9,straight snoot, wedge,diverter,shoe/plate an I still run a rock grate. Runs very well
Devils advocate here.
So there is no way, with a properly tuned loader, it could work better?
The inducer and shoe is doing the job of the loader. JMO.
GT
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If I would get a noticeable diff in speed/handling, I might ad it but I like the way the stock grate helps keep out debris more than 200rpm or whatever low expectations it might produce. With all the other goodies, I'm satisfied.
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Ok I'm gonna give it a try. On my Gullwing I have tried two different loaders MPD vs B1. This is my conclusion after testing. Mpd loader without nos I would run 6400rpm without nos at 98 mph, with nos I ran a 106 but has a problem unloading, B1 loader boat will only do 96 on motor at 6200 and ran a best to date to 113 with absolutely no unloading problem. Conclusion is you need to pick the right loader for what your hp range is. If I were to race everyone on motor i choose mpd but I don't I set my boat up for nos and Chris did a awesome job with his loader and could not ask for more. So in my mind you can overload the pump and loose mph. Don't stick a big loader in your boat if you can't push the water.
"RTCP"
Is your MPD loader a blocker style?
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Is your MPD loader a blocker style?
yes sir
"RTCP"
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Here is our current thinking.
Jet pumps are not able to draw water in on their own; they need to be fed water. A jet boat feeds water to the pump by three means.
The shape of the keel has the most influence on loading the pump, but only while at speed. An object moving through the water displaces the water, causing a point of low pressure immediately following the displacement. Everything in nature attempts to return to equilibrium and the water rushes to fill this low pressure area, attempting to return to equilibrium. In a jet boat, this point of low pressure is immediately following the keel, leading up into the pump intake, just before the loader/rock grate pad. The Coanda Effect describes how the water “entrained” to the surface of the intake follows it up into the pump. The Coanda Effect is described as the phenomena in which a jet flow attaches itself to a nearby surface and remains attached even when the surface curves away from the initial jet direction. If the surface is too severely curved, the water will not follow the surface, but will bend slightly and detach from the surface.
The shoe acts as a splitter to scoop water into the jet pump. A high pressure area is created above and slightly in front of the biting edge of the shoe and a low pressure area, as evidenced by the cavitation burn on the ride plate, is created below and slightly behind the shoe. The high pressure area just above the shoe feeds the bottom of the impeller.
Note: the cavitation burn pattern on the ride plate is also influenced by the parting line between shoe and ride plate, the countersunk fasteners holding the ride plate on, and the biting edge of the shoe itself. Condition of the biting edge can also contribute to the ride plate cavitation burn pattern.
A loader is a compilation of these two effects. The leading edges and top surfaces of the ramps act like a shoe, whereas the bottom surfaces resemble the curvature of the intake and assist in loading via the Coanda Effect.
In most cases, a dropped keel will load the impeller harder at the top than the shoe can load the impeller at the bottom. The design of the loader should complement the type of hull, intake design, and installation of the intake/pump in the boat. There are many variables to loader design: length of the ramps (both leading and trailing edges), angle of attack, location, etc. One design of loader does not fit all applications. Not all loaders fit all intakes either.
With that being said, our philosophy on loading jet pumps is; every effort should be made to load the impeller appropriately for the horsepower available without overloading the pump. A properly loaded pump helps to develop more lift on the hull and build more thrust.
Some comments were made about losing RPM with the addition of a loader. If the pump is not being properly loaded, the inlet eye of the impeller is not receiving enough water to bite into. Air ingested into the pump is compressible as is aerated water. A mixed flow pump, such as a typical Berkeley jet pump, works by accelerating the velocity of water within the pump and converting that energy to pressure. Any time air is ingested into the pump, the impeller stops accelerating the water, bowl pressure and thrust drops, as does resistance against the impeller. The result is an increase in RPM.
Aerated water can be ingested by the impeller from many sources. The first and most obvious is when the intake opening physically loses contact with the water. For this reason, white water and circle boats that operate in rough water will work better with a different loader design than a drag boat. Much less obvious is driving through aerated water as in the case of a drag boat driving through the wash of the boat that made the prior pass. More importantly to this discussion is aerated water that is the result of a disturbance in the laminar flow of the water ahead of the impeller. Rock grates and turn fins are just such examples. One racer campaigning a Rogers in NJBA picked up substantial intake pressure, and therefore bowl pressure (see GT’s earlier post regarding NPSH), by cutting off the turn fin with a Sawzall in the pits. This made such a drastic difference on performance that the rough cut was further dressed and filled for additional gain.
This brings me to my strong dislike of rock grates. Rock grates are constructed with six 1/4" by 1” flat stock welded vertically to a pad that bolts to the intake. If you add up the restriction created by the rock grate, it is actually more than the effect of a 1-1/2” bar covering the opening of the jet intake. Each of the six bars of the grate creates its own turbulence and aerated water, immediately in front of the inducer (if so equipped) and impeller, depriving the pump of a clean(er), more laminar flow of water. This explains jyeager’s loss of 200 RPM. The rock grate is disturbing the water flow to the impeller, allowing it to slip. A car analogy is “riding the clutch.” The clutch pedal is partially depressed while driving which partially disengages the engine from the transmission. There is less resistance on the engine and the RPM increases, however the same amount of power is being transmitted to the wheels to drive the car.
In capogniracing’s case, the MPD loader is a blocker style and the B1 Racing loader is not. A blocker style loader does exactly what the name implies, it blocks some of the flow to the impeller. The concept is that a ramp is incorporated into the loader do deflect a portion back out of the jet intake. This has the effect of creating more lift of the hull. Another effect, and depending on your perspective, can be either positive or negative, is the impeller is deprived of water. The blocker ramp creates a shadow as the water is deflected out of the intake. This shadow is an air cavity in the intake and suction housing which is not helping to load the impeller. When a naturally aspirated pass was made, the partially loaded impeller slipped, allowing the engine to RPM higher, where it made more horsepower. More work was being done. While making an NOS pass, the engine was producing substantially more power, causing the impeller to slip more. The non-blocker loader loaded the impeller harder, more efficiently converting the NOS horsepower to thrust and the boat increased speed. While running the non-blocker loader naturally aspirated, the pump absorbed more horsepower than what the engine was capable (compared to on the NOS). The result was a loss of 200 RPM and 2 MPH compared to the blocker style loader. While making a NOS pass, the boat liked the non-blocker style.
In both cases, the pump was working more efficiently and therefore requiring more horsepower to turn the higher RPM. Our solution would be to cut the impeller so that the pump would operate at the RPM where the engine makes peak horsepower. If the pump stalls the engine at peak horsepower, more work is being done. Ultimately, the boat will be faster all around. In some cases, depriving the impeller of water (pseudo cavitation) can actually cause damage to the pump. Our opinion is that blockers are dated technology, however, if you absolutely have to have one... the customer is always right.
Really, this just scratches the surface of loader theory. There is a lot more to setting up a boat than just bolting in a loader. I would like to emphasize a word of caution here. In the case of a heavy mini-day or day-cruiser, cutting the impeller will drastically hurt launch. It is true that a smaller impeller reduces efficiency at every RPM compared to a larger impeller. But it is also true that a pump operating at a lower capacity it is designed for is also inefficient. In this case, it is better to error with a larger cut impeller. Consider the application, just how much time is spent at peak RPM? A larger cut impeller will launch harder and have better cruise characteristics. If this is where you spend most of your time, but with an occasional full-throttle blast, select an impeller cut to enhance your boating needs.
ANOTHER WORD OF CAUTION!!! LOADERS, AND THE ATTACHING HARDWARE, NEED TO BE CHECKED FREQUENTLY! Loaders are the one part where upon failure, the WILL crash. There is a tremendous load being placed on the loader, the bolts holding it, and the intake itself. You should inspect your loader frequently for cracks that might form, in the verticals, just after the loader pad where it attaches to the intake. Corrosion is another issue and if not kept in check, can render a loader unsafe. The intake should be drilled and tapped all the way through to 5/16-18UNC 2B. Inspect the torque on the fasteners every trip. Only grade 8 fasteners should be used to attach the loader. Stainless steel fasteners are between a grade 2 and a grade 5 for strength and should not be used to attach a loader. At least the rear two fasteners should have nylon locking nuts installed on the inside of the intake. Install nylon locking nuts on all four fasteners if there is no interference with the oil pan. Replace the fasteners every season to avoid corrosion fatigue. Use a lot of anti-seize to facilitate easy removal of the fasteners.
Cheers,
Joe
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bam! O0
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Any one know where I can find a Jack McClure?
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MPD
Marine Performance Designs
1760 Monrovia Ave, A-7
Costa Mesa, CA 92627
(949) 631-2040
Dan'l
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Saving for later...
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Thanks anyone got a split bowl they wanna part with?
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