Prop lost pitch?
 

After experimenting with several props i finally had found the right one. Mirage 23 plus. 4700 RPM, 61mph. Now is seems this year my wot is around 5100rpm. I seem to be 400 rpm higher or so at most cruising speeds to maintain the same speed as last year. It is like im running 21+ now. There have been no changes to the boat. could my tach be off now? should i start trying different props again?

Props do fatigue, and lose their pitch... but 400 rpm seems like an awful lot! Did you hit something with the prop? Or did it get droped or banged into?

Chris

I'm betting its the tach. It could actually be reading correct now and was off before. Also, with a 502, you should be running 5100rpms anyway.

no prop is like new, on the engine cover it recommends 44-4800 rpm. This is the older carb 502 mag. not mpi.

Get your hands on a digital tach to verify your tach readings.

Chris

ethanol..?

502mag recommended WOT for both carb and efi is 4600-5000rpms. For the best performance, you want to spin it at the top of the wot range.