I have a 222 Mariah SHabbah with a fuel injected 7.4L that I bought in California. We drove the boat down there and it ran fine. Brought the boat to Lake Powell and lost 1000rpm. I'm only able to get to 4100. The boat has a Volvo DPX-A outdrive with 1.78:1 gears, which is the lowest they offer for the outdrive. It also has E-2 props, which is also slowest prop. Is that all I'll get at 3300 ft or do I have other issues?

That sounds about right to loose around that much rpm at lake powell from CA, Normaly most boats will drop pitch around 4 pitchs as an avarge up there, If you where going to run up there all the time then you would need to have a different set of gears installed, Or find a good used drive, And have it laying around to install it before you head up to powell I am thinking it ran like this on the first day of running. Or maybe it was after buying some gas up there or mayby you bought gas on the water? To feel safe you could try pulling the fuel filter off and dump it in a clear jar of some kind and look for dirt or water sitting at the bottom of the jar if it started running like this some time later. Anyway have a good time up there and be safe and good luck with it.

I lost 1500 RPM with a fauled plug !?

Just a guess.

Thanks for the advice. Does anybody know if they make an aftermarket prop for that outdrive? If so that may be the answer to my problems.