Re: Sudden drop in rpm’s

[Don]

Hmmm, OK, well I am assuming no amount of fiddling with carb adjustments makes any difference…Can you estimate how much the WOT has dropped? I like the idea about an exhaust blockage, maybe this engine was sitting before you got it and has a nest up in there. Yeah, I probably wouldn’t mess with that exhaust cover, especially if the engine has seen salt water use. You mentioned the compression numbers haven’t changed. How does the engine run otherwise? Starts and idles OK, runs smooth at higher speeds?
You might want to try cleaning the plugs up, then running it hard at WOT for several minutes, then shut it right down and pull the plugs to have a look…Maybe there is a slight water leak into the combustion chamber(s), or perhaps there is an ignition fault weakening the ignition causing the RPM drop. This is where those neon testers would come in handy, although a little tricky to use and monitor on the water at WOT.