Choosing a prop at elevation

[MntPenguin]

I just brought my boat from sea level to a lake that sits at 8400ft in elevation. I am having difficulty getting up on plane and it was suggested by a friend that I need a different pitch on my prop.

She's a 17ft Boston Whaler with a 90hp Evinrude. The current prop is a 15.5X13. Any suggestions as to what I should be running?

 

[WesNewell]

Estimated loss of hp is 3% per 1000' of elevation. So your 90 hp engine is now ~67hp at 8400 ft. elevation.. I'd try an 11P. Or try one of the many prop selectors you can find online.

 

[Scott Danforth]

welcome aboard.

in addition to the prop change, you need to change the jets. information is in your factory service manual.

 

[Sea Rider]

Before changing current prop need to go for a wot run as will be loaded and report your max wot rpm achieved with a tach to know how many prop pitches need to drop. At high elevations will need a carb re jetting if being a carbed motor and less pitch prop for the motor to work much better, not top though as at sea level. Is that a carbed, EFI or Etec model ?

Happy Boating