Rivertender
Member
It should still rev out above 3500 rpm even with open chamber heads . Street raced for years and any big block would rev to 5000 easily, possibly timing or fuel
comforting. Thanks. 3400 is just wrong.
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It should still rev out above 3500 rpm even with open chamber heads . Street raced for years and any big block would rev to 5000 easily, possibly timing or fuel
Even pulling a trailer up a hill? I don't think an auto with a transmission is a fair comparison to a heavy boat trying to get on step.
@Rivertender, I read some of your earlier posts on this and another forum. It sounds like you replaced the distributors with EST Voyagers before the head swap. Is that the case?
...............................I am thinking you might have me confused with another member? I am not familiar with that brand and I nor the mechanic have never fooled with distributors.
Your symptoms as others have mentioned could easily just be a timing problem.
The Voyager distributors work great in jet boats (my experience with them), but I have my doubts with an i/o application. They do not hit their full advance until 3600 or something like that. Jets don't care as it is just a pump in front of a nozzle (restriction). The original Thunderbolt distributors can achieve full advance as low 2000 rpm.
Have you checked the timing with your engines loaded?
......................................mechanic has them at 10 degrees, claiming spec is 8 to 10. I assume loaded means underway? I was on the bridge while mechanic down below, not sure but don't think he checked them underway.
We are all trying to help.
Even pulling a trailer up a hill? I don't think an auto with a transmission is a fair comparison to a heavy boat trying to get on step.
@Rivertender, I read some of your earlier posts on this and another forum. It sounds like you replaced the distributors with EST Voyagers before the head swap. Is that the case?
Your symptoms as others have mentioned could easily just be a timing problem.
The Voyager distributors work great in jet boats (my experience with them), but I have my doubts with an i/o application. They do not hit their full advance until 3600 or something like that. Jets don't care as it is just a pump in front of a nozzle (restriction). The original Thunderbolt distributors can achieve full advance as low 2000 rpm.
Have you checked the timing with your engines loaded?
We are all trying to help.
I think he is talking about when the engines are under load. They simply wouldn't make enough power with changing the heads from CC to OC. Compression ratio will drop too much.It should still rev out above 3500 rpm even with open chamber heads . Street raced for years and any big block would rev to 5000 easily, possibly timing or fuel
It is cheaper to start with the routine maintenance items first to see what effect that has on issues such as running a little on the warm side. Impellers are wear items that need replacement on a schedule. Otherwise you have overheating when they wear out and breakdown.
Can you post the pictures he sent you along with any explanation of what they are pictures of?
This was the 3 year old post that mistakenly made me think you replaced your distributors with Delco Voyager EST's.
Marine Voyager engine parts - The Hull Truth - Boating and Fishing Forum
It sounds like you didn't so fair enough.
Another post that threw a flag for me was from last spring when you commented that the boat wasn't used in 2021 and the fuel in it was old. It sounds like that wasn't corrected and it can be a big problem when trying to make power with your engines.
Information that you may not consider to be important can easily mislead others when left out and send them in another direction. It was the reason I looked into your earlier posts. Nothing more.
Hoping for a simple resolution for you.
I would like to THANK EVERYONE here for their effort to diagnose my low rpm problem.
A quick recap of the issue:
- a year's work and a ton of money fishinsed the refurb of my motors
- sea trial only delivered 3400 rpm WOT, not the expected 4000 to 4400
- mechanic response:
that's a good rpm-right where it should be
your engines are old and tired, can't expect much more (1,000 hours}
your bottom is dirty with growths
your gas is no good
My monthly diver did say that the bottom needed attention given that the bottom paint was 5 years old in St Pete, FL.
The gas was old, for sure. 16 months-ish.
Had the bottom repainted. BTWay, when my boat came out, the bottom was astonishingly free of growth. People in the yard were amazed that the bottom was clean. 1 guy even took pictures of the bottom. I am told by most everybody - 3 years is about all you can expect around St Pete for a bottom paint to last. Paint was Trinidad Pro. I, as everybidy does, have a diver scrub the bottom monthly. Attached pictures (sorry for the sideways-they are correctly positioned in the original file and I don't know how to fix it} are of the bottom when it came out after 5 years -it was powerwashed but looked not much different before.
Had the gas removed and put fresh gas in. Fuel remover guy tested the fuel and said one tank was borderline bad and the other was bad.
Put new fuel filters on.
Sea Trial 5 days ago - shoved the throttles up and she got to 4050 rpm. Not the perfect 4200 to 4400, but I am nevertheless thrilled.
Given that the bottom was so clean, it had to be the fuel. I know now to keep my tanks filled with fresher fuel.
Many, many thanks again to everyone for your good advvice and efforts to help.