RPM issues

[QUANANGIE]

We have a 1997 Speedster. We start the boat, let it run for 5-10 min before driving. We cannot get past 4000 RPM, then one engine revs to 7000, and the other drops to 3000. The boat seems to be working so hard. We stop the boat, take a break for 10 min, restart the boat and it runs perfectly normal. At 4000 RPM we are flying, where as before the 4000RPM we are at idle speed. What is the problem? This has happened 2x now. Thank you for your time!

 

[gokeeper]

There are a range of possibilities, It sounds like varying degrees of cavitation, especially is you are seeing varying performance at different RPM's. It could also be a fuel issue or combination of issues, (fuel, cavitation, ect.) Have you checked the pumps for stuck objects, impeller condition, and also look at the carbon seal ring in the through hull fitting. Look at the fuel filters if they are see through and see if it is starving for fuel.

I would start with the condition of the pumps, impellers, carbon rings and boots. How does it start and perform out of water on a hose?