Prop Pitch Question at Altitude

[R. Duzac]

I was up at Bullards Bar this weekend and I thought there was something wrong with my motor. I didn't think we were at that high of altitude but I rarely have my boat much above 1000' see level. After talking with most everyone else they recognized the power loss as well.

I have a 1997 - 18'.6" Viper Cobra with 200 EFI Mariner, 25 Pitch Prop. At See level I run 5800 RPM, ~62 MPH
At Bullards Bar I was running about 5400 RPM, and ~55 MPH

Is there a calculation for Prop Pitch/Altitude?
Do you pitch down the prop for higher elevation lakes?

Thanks,
Rene

[bassmonkey]

You will feel a power loss with an EFI for sure. I can feel the difference between Folsom and Bullards and I have a Optimax. You can compensate by dropping to a 24p or 23P prop.

[Riplip]

I believe it is one inch of pitch per 1000ft of elevation, so if you run a 25p normally you would want a 23p at 3000ft.

[R. Duzac]

Thanks,
Very helpful.

Rene