I had the same issue with my stock 454, I changed the control module in the distributor to a brand called flame thrower, it worked great until I revved the engine to high and destroyed it 👎! Cast pistons and peanut port heads don't like to be revved high, I now have a built motor with 781 heads and she runs at 5500 with no problems


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I have the same boat but the commander version  (that boats been built by everyone )and my stock 454 only revs to 4400 at 53 mph on gps

I have some updates since I was able to work on the boat a bit this past weekend.

I replaced the fuel filter checked the timing, these were the two main things I was looking to get done.  At idle the timing was around 20 deg advanced (I don't know for sure since the indicator stops at 16).  With the timing shunt plugged into the dist the initial timing dropped to 8 degrees, unfortunately the dist was locked in place due to corrosion so I couldn't adjust the base timing up to 12 deg (1st fail).  Knowing that I couldn't adjust the base timing I decided to check the advance as i revved the engine.  Around 3k it moved up a little but probably only up to 24 deg, this was showing total advance from 20 ish at idle to 24 ish at 3k RPM.  This has me thinking the module is bad so I already ordered a replacement.

The boat runs well enough so I took it out on Friday and it ran the same since the day I got it.  Fires right up and limits out at 4200 RPM. 

Saturday morning I decided to put on the new to me Holley 750 DP and hoped that would make some improvements that day on the water.  Once it was all plumbed up I turned the key and gas was just pouring out of the J-tube (2nd fail).  The front float appeared to be stuck, and no matter how much I smacked the carb with a wrench it just did the same thing.  So the new carb came off and the old one went back on. 

The boat runs fine and she was always meant to be a cruiser so I hope I am not chasing more RPMs and throwing parts into her if there will be no change in the end. 

At this time, I have a new flame arrestor ordered (thinking the one on there may be limiting air flow).  A new ignition module on the way, and the new carb will be rebuilt soon.  All those parts will get changed out, and I will adjust the base timing when I hit the water in a few weeks so hopefully there is an improvement then. 

So I just did some research and the carb I got is a 800cfm not 750 like the guy said. The jetting in there right now is 72f and 87r with 31 squirters front and back. Is this likely way too much for my stock 454? 

List number 9022.

This is like asking if you have the right shoes on.  Lol

What is the list number?

GT

Those jets are stock to that carburetor. If anything, they would be too small.

Let me look into a few things.

That's a really nice carburetor btw.

GT

Thanks GT. just checked again and the power valve is a 7.5.

I was able to make it out to the river this weekend and got some work done on the boat. The good news, I was able to make some progress and the motor seems to be running stronger. The new ignition module I bought didn't work out of the box so I stayed with the old one and bumped up the initial timing to around 14 degrees.

Before I went out I bumped up the jet sizes on the new carb to 76 front and 91 rear then dropped the power valve to a 5.5. I got the idle dialed in with the air bleeds and the motor pulls really good vacuum at idle. When I got out on the water she runs strong all the way through the primaries. But when I get into the secondaries the revs get up to 4400 then seem to fall flat. It feels like the motor has more in it but may be starving for fuel.

At the very top end the boat seems to surge and bounce from 4200 to 4400 with some popping. Is this a lean issue?  I am leaning toward changing the powervalve to the stock 6.5 since the motor made nearly 18 inch of vacuum at idle (on the trailer). I didn't have time to pull plugs when I got off the water to see if it was lean this is just a hunch.

Any input is appreciated.

What was the vacuum at the highest throttle setting?

The power valve does not need to be higher vacuum. There is very little engine load at 6.5" hg.

A jet boat engine has a linear torque curve, so the engine load gets higher as the revs go up. Once the torque is exceeded, acceleration stops.

What was your fuel pressure at WOT? I don't care if you leave the jets out of it completely, if you don't have the fuel volume/pressure, it will ruin itself out of fuel.

GT

Unfortunately I don't know what the vacuum was at when I was WOT, all I have is a handheld vacuum gauge which I used to set the air bleeds.  I could try to get a length of hose and bring it up to the front of the boat to have a look while I am driving. 

Also, I wasn't able to get a look at the fuel pressure gauge while running WOT, it was at 6psi at idle but I know that means next to nothing.  The fuel pump is a carter vane style which I assume is original to the boat. 

As I mentioned earlier the motor felt a lot stronger with the new carb and changes so I think I am close.  I have been planning on taking the boat to a professional over this winter for a once over, so I may leave it in capable hands to fine tune the carb.

GT as always I appreciate your help, and I will update if any changes are made.

A couple of suggestions:


The surging & popping at WOT 'sounds' like a lean condition.
Seems like you are getting timing advance, 24 deg. all in sounds o.k., so I would just concentrate on the fuel system.
Have you checked the spark plug coloring yet?  It's a good indicator of, among other things, if you are running lean or rich.
The best readings are obtained from new plugs . Change them out, run it through the entire rpm range, & see what you get initially. It'll help with your diagnosis.
Make sure the plug wires are good. Older wires that have dried out or cracked insulation can potentially fail under higher rpm with a load.
Have you pulled the secondary bowl to see if there is any junk in there? Also check the secondary throttle blades to see if they are opening all the way, & that all your linkage is moving freely.
The power valve is already doing it's job at WOT since you are probably pulling 1" or less of vacuum at that point. You should be good with a 6.5 or 4.5……..
At any rate, it wouldn't hurt to pull the carb & do a rebuild.  You could do that yourself. Holley rebuild kits are pretty inexpensive……

I didn't get a chance to check the plugs after last trip but will make sure to check them after some runs when I go out next weekend.  I put all new wires/plugs/cap/rotor on at the beginning of the season so those shouldn't be an issue.  The new to me carb was just rebuilt and I am getting full travel on the throttle. 

Next trip out I am going to up the jet sizes again and try to raise the floats a little, hopefully having more fuel in the bowls from the get go will allow them to keep up with the demand.

Again thanks for the input and I will update accordingly.

Does anyone have plug recommendations for a gen V 454 open chamber/peanut port heads.  I can't remember what I put in at the beginning of the season, and not sure if the gen V makes a difference.

EDIT: I'm fairly certain the plugs are Delco R43T, that seems to ring a bell but I can check for sure when I get home.  Is that a hot enough plug for the open chamber low compression setup I have?

Was it popping out the carb or exhaust.....

Disclaimer: I've only played with BBCs in cars, not boats... what I'm about to say applies to automotive but I don't see why marine would be different.  The following is based on the distributor having a mechanical advance, not electronic...


A typical GM HEI should have more like 14-18^ or so of advance from idle (I've seen it vary from model to model) .  If base is set at 20 you should see 34-38 total at 3000-3500.  Depends on weights, springs and stoppers.  If you're only seeing a 4^ advance it sounds like the mechanical advance mechanism is stuck, possibly corroded given that distributor is locked in place to the block. 

That being said, 24^ sounds awfully low to me.  Street cars with pump gas and 10:1 compression usually run in the 32-34 range as a starting point and dial it in from there.  The 1st thing I'd do is check to make sure the advance is working correctly and try adding some timing.  Go in small 2^ increments and see how that affects the top end.  Check plugs for signs of detonation between adjustments.

I've seen this type of issue in automotive a few times and this was the answer, but like I said I've not run a BBC in a boat.  Guys with more marine experience please correct me if this doesn't apply. 

All good ideas but this is a 8 pin hei. All electronic so there all no weights it's all build into the module. I may bump up initial timing a bit more but she is for sure starving for fuel.




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Isn't that a rich condition?  Or misfire? Chime in guys I'm not so sure a larger jet is the way to go..... I've known dizzys w hairline cracks  causing misses and sometimes acting like it's the module..... are u running super slick 8mm put together yourself wires? Also what plugs/ gaps I've found gms to be very happy w stock ac delcos not split v triple crazies lol  do u