Sleekcraft SST max 4,000 RPMs on water

« **on:** June 02, 2012, 07:52:12 PM »

Hi guys! So I didn't get to any of the work I wanted to over the past year because work has been slow. However it's picking up for the summer which means new parts . Last year we all talked about messing with the secondaries and timing and cleaning the jets etc. I think I found the problem of why I can't get any faster on the water. I'm very poorly educated on engines and jet pumps but I found this chart on the PJB site,

http://www.jetboatperformance.biz/pages/calculator.html

So while I'm trying to become familiar with motors and jets, here is my understanding from this chart, PLEASE CORRECT ME IF I'M WRONG. So I really have no clue which impeller I have but I'm guessing it's an A. For all I know, the motor is a stock 1986 454 which produces 230 HP. It has a Holley marine 715 CFM carb if that info helps at all. While looking at the chart on the PJB site I noticed that the correlation on the chart is 4000 RPMs, around 230 HP with an A impeller. So the way I am understanding this is that this is the highest my boat will perform with the current combination. I appreciate the feedback and any help you guys can offer. I'm trying to get this thing to run around 60-70 mph depending on financial circumstances. Thanks guys!

« **Reply #1 on:** June 02, 2012, 08:42:24 PM »

how fast is your boat now?

« **Reply #2 on:** June 02, 2012, 09:10:45 PM »

Ive had it to 44 and when i try to floor it, it wants to bog down

« **Reply #3 on:** June 02, 2012, 10:56:48 PM »

OK just for clarification.
Your saying it turns 4000 RPM on the water, at 44 mph, with partial throttle. Then when you floor it, it bogs down. Is that right ?

« **Reply #4 on:** June 03, 2012, 10:00:48 AM »

« **Reply #5 on:** June 03, 2012, 10:01:47 AM »

Quote from: propless on June 02, 2012, 10:56:48 PM

OK just for clarification.
Your saying it turns 4000 RPM on the water, at 44 mph, with partial throttle. Then when you floor it, it bogs down. Is that right ?

Yeah

« **Reply #6 on:** June 03, 2012, 11:59:28 AM »

Quote from: NoRestraint on June 03, 2012, 10:01:47 AM

Yeah

Check for the timing issue mentioned in the other thread and check to make sure the secondaries are working on the fuel side in the carburetor, betting on the timing being FUBAR

One thread bud...Your making my head hurt.

GT

« **Reply #7 on:** September 04, 2012, 10:03:54 PM »

Welllllllll, I've adjusted timing to 34 btdc full advance, made the secondaries mechanical and confirmed they are functioning and I'm still only turning about 4100 RPM and 47 mph. Gonna replace the plug wires this weekend to make sure it's not an electrical issue with them grounding to the headers. Any possibility that my deal may be a Jet issue?

« **Reply #8 on:** September 04, 2012, 11:19:55 PM »

How did you "make" the secondaries mechanical?

This is my first time reading this thread. If it lays down before wide open throttle...you've got a fuel delivery issue. While its possible the coil isn't charging long enough to light it at higher RPMs, it's unlikely. We can check, very simply, to determine whether it's fuel or ignition though. Next time out, after warm
Up...get on the throttle until it starts to bog down.....turn the key off and keep the throttle where it is until the engine stops turning....then pull a plug. If its dry and white, you're running out of fuel. What fuel pump are you using? Post some pictures of the pump and the line/carb setup.

« **Reply #9 on:** September 05, 2012, 07:16:18 AM »

Start at the simplist solution first. Fuel filter would cause the condition you're having. Then check fuel pump, do you have a fuel pressure gauge? If the pressure drops during the bog condition it could still be the filter, but if you change it which is cheap then probably pump. If there is a water seperator replace that filter as well.

« **Reply #10 on:** September 05, 2012, 09:37:31 AM »

I agree on the fuel issue. Also pull the fittings from the bowls where the fuel lines go in for the sintered bronze filter and spring. If it hasn't been done already, remove them and properly dispose of in the trash. Stick with external filters.

And the only way I've seen a Vac sec'y carb "made" mechanical is by bending the linkage from the primary to the secondary (That's there to force the secondary closed and prevents it from opening by itself under vacuum) around its plate forcing it to open, mechanically, with the primary.

There may be some other methods out there that I haven't seen, but honestly, none are a good idea even remotely. Vaccum Secondary carbs do not have secondary accelerator pumps nor metering blocks on the secondary side, relying totally on vaccum to not only open the secondary (if even needed), but also allow and control needed fuel flow to the secondary squirters. Simply forcing the secondaries open constantly will do nothing more than create a tremendously over lean condition at all throttle positions (which you will probably find quickly when you read your plugs like Pat said), will cause the "bog" you are describing, and likely cause backfiring and popping at full throttle.

Ray

« **Reply #11 on:** September 17, 2012, 05:10:43 PM »

Thanks guys. I put a tiny but and bolt on the little half moon deal that opens the secondaries so that the primary rod would pull them open at a certain point. I've got a Holley black but my pressure gauge is not in an area that I can see while driving. At idle I have 14 lbs of pressure (overkill I know) but I'll start with changing the exterior filter and throwing the internal ones away. I'll let you guys know what happens within the next couple of weeks! Also where the hell is the closest place without a dam speed limit so I can test it out? I live in la Crescenta about 10 miles north of LA

« **Reply #12 on:** September 18, 2012, 06:59:59 AM »

Parker Strip about 300 miles. All So Cal lakes have 35mph speed limit. After the guys at Castaic looked the other way for HTM to test their boats at high speed and we all know how that ended, you best keep it within 10 mph of speed limit.

« **Reply #13 on:** September 18, 2012, 08:03:33 AM »

14 lbs of fuel pressure will force by the needle and seat in a Holley carb, it should be in the 6-7 lb range. 14 lbs is probably 'flooding' the motor, had this happen with a bad regulator, and would only run wide open, but this doesn't sound like the problem. Sounds like fuel starvation, like others have said.
A bone stock '78 454, 220 hp (K30 smog motor) turned the pump to 4400 rpm on the primaries on a Q-Jet, at Silverwood (~4000 ft), so even if it is some what lean, it should pull more than 4000 rpm, but I wouldn't run it lean like that, lean is baaaad.

Where is the fuel pressure gauge at? Most Holleys are on the fuel rail between the primaries and secondaries, if yours is before a fuel filter, and the filter is plugged, you can get high(er) fuel pressure readings. What fuel pump? Mechanical? Electric?

The impeller charts are a guide, and not exact. An 86 220-230 hp is net, in a truck. the same motor is 320-330 hp gross when used in a boat. This combo should be capable of 44-4500 rpm with an 'A' impeller, possibly more.

The Pacific has no speed limit either

Thats all I got

Daniel

« **Reply #14 on:** September 18, 2012, 09:00:41 AM »

You also have the middle of Elsinore, closer

« **Reply #15 on:** September 18, 2012, 09:32:27 PM »

Quote from: mash on it on September 18, 2012, 08:03:33 AM

14 lbs of fuel pressure will force by the needle and seat in a Holley carb, it should be in the 6-7 lb range. 14 lbs is probably 'flooding' the motor, had this happen with a bad regulator, and would only run wide open, but this doesn't sound like the problem. Sounds like fuel starvation, like others have said.
A bone stock '78 454, 220 hp (K30 smog motor) turned the pump to 4400 rpm on the primaries on a Q-Jet, at Silverwood (~4000 ft), so even if it is some what lean, it should pull more than 4000 rpm, but I wouldn't run it lean like that, lean is baaaad.

Where is the fuel pressure gauge at? Most Holleys are on the fuel rail between the primaries and secondaries, if yours is before a fuel filter, and the filter is plugged, you can get high(er) fuel pressure readings. What fuel pump? Mechanical? Electric?

The impeller charts are a guide, and not exact. An 86 220-230 hp is net, in a truck. the same motor is 320-330 hp gross when used in a boat. This combo should be capable of 44-4500 rpm with an 'A' impeller, possibly more.

The Pacific has no speed limit either

Thats all I got

Daniel

X2, don't confuse pressure with flow....6 lbs max.

NoRestraint

Sleekcraft SST max 4,000 RPMs on water

mobboss

Re: Sleekcraft SST max 4,000 RPMs on water

NoRestraint

Sleekcraft SST max 4,000 RPMs on water

propless

Re: Sleekcraft SST max 4,000 RPMs on water

NoRestraint

Sleekcraft SST max 4,000 RPMs on water

NoRestraint

Sleekcraft SST max 4,000 RPMs on water

GT Jets

Re: Sleekcraft SST max 4,000 RPMs on water

NoRestraint

Re: Sleekcraft SST max 4,000 RPMs on water

lbhsbz

Sleekcraft SST max 4,000 RPMs on water

74RogersBubbledeck

Re: Sleekcraft SST max 4,000 RPMs on water

IRRebel

Re: Sleekcraft SST max 4,000 RPMs on water

NoRestraint

Sleekcraft SST max 4,000 RPMs on water

74RogersBubbledeck

Re: Sleekcraft SST max 4,000 RPMs on water

mash on it

Re: Sleekcraft SST max 4,000 RPMs on water

76NORDIC

Re: Sleekcraft SST max 4,000 RPMs on water

GT Jets

Re: Sleekcraft SST max 4,000 RPMs on water