cardealer30

I have 1 engine that will only get to 4400 rpm the other hits 4800-4900 they run even until about 3000 rpm. I have had a performance shop talk me into valve job, new lifters,rebuild carbs because of weak leak down test,,,still runs exactly the same
compression excellent in both.The props look identical but have not switched them yet

Any ideas or help would be great

Scott

Knock sensor????

Lmarth

The "Performance" shop rebuilt the carb because of a weak leakdown test???? I thought I'd heard it all. You don't indicate whether the two engines worked fine and now the one won't pull past 4400 rpm. Don't know how many hours are on the motor but a fuel pump with a diaphram that's tearing would do what you're seeing. You should have a vent on top of the fuel pump with a plastic hose going to the carb. Do you see fuel bubbles in the hose. Don't know what ignition is now on the motor. An advance problem could also be the culprit. If it's the stock Thunderbolt, they usually either work or not. Again, I don't know what's been done to your motor. What I do know is that I'd probably try to find someone else to work on my boat. There are always two sides to every story, but I'd be a little suspicious of your "performance" shop. Just my $.02

cardealer30

Thanks lmarth,,
no he didnt rebuild carbs because of leak down just recomended it to me while we were doing valve job,,,ive only had the boat for about 1month and put about 10 hours on it,, boat has about 220 hrs on it,,,it has run the same before and after all this work done,,,still dowm 400 rpm on one side but doing about 69 mph gps

John B

Check valve spring problems with 500 HP's (posts).

dreamer

i just pulled mine apart and found a trashed cam lobe on the engine that was down on rpm

cardealer30

thats scary,,,how low was the rpm on that motor??