Prop pitch for high altitudes?

[Madhatter73]

Good day everyone! My uncle just bought a place in Jackson Wyoming and took his 2012 Bennington 2275 RL, ESP with a F150 Yamaha four stroke up to run it on Jackson Lake. He resides in Nebraska which is only 1000 ft. above sea level and Jackson Lake is 6772 ft. above sea level. Here in NE the boat runs great with a 15 pitch prop but will only run 28 mph and 3800 rpm's at Jackson Lake. He tried a 13 pitch which brought the speed up to 32 mph but he is still only getting 4200 rpm's at WOT.

Anyone on here have experience in the higher elevations? He is going to try an 11 pitch to see what happens but I don't think he is going to get his full rpm's out of it.

Any thoughts or advice would be greatly appreciated!!

Thanks!

 

[Jim_R]

I'm betting that he only gets another 400 RPMs from dropping to 11 pitch. I assume his Yamaha is EFI, correct? If not, he will need a tune for the altitude.

 

[Madhatter73]

I'm betting that he only gets another 400 RPMs from dropping to 11 pitch. I assume his Yamaha is EFI, correct? If not, he will need a tune for the altitude.

Thanks for the reply Jim. Yes the motor is an EFI. I was thinking about the same as far as the RPM gain. Could you maybe elaborate on what consists of the "re-tune" for altitude. Much thanks sir!

 

[Geoffrey & Brenda]

Since the engine is an EFI it does not need to be retuned, the computer uses a barometric pressure sensor for altitude compensation.

On a carbureted engine, the retune would be changing the main metering jets in the carbs. and perhaps some adjustment to the ignition timing.

 

[Madhatter73]

Since the engine is an EFI it does not need to be retuned, the computer uses a barometric pressure sensor for altitude compensation.

On a carbureted engine, the retune would be changing the main metering jets in the carbs. and perhaps some adjustment to the ignition timing.

Thanks. Familiar with the carb motors and the jets just not the EFI stuff. So sounds like he might have to have the computer reprogrammed or something if he is going to keep the boat up there. My best bet sounds like having him get a hold of a Yamaha dealer up there somewhere since they would be more familiar with their altitude.

Thanks for the info and have a great day!

 

[Remediation]

Please let us know the solution and outcome.

 

[kaydano]

Didn't know altitude made so much difference. Maybe the performance topic needs to have altitude as an entry. Could explain some differences.

 

[Wild and Free]

Didn't know altitude made so much difference. Maybe the performance topic needs to have altitude as an entry. Could explain some differences.

Elevation is one of the biggest performance issues with many different engines. The lack of oxygen the higher the elevation directly effects engine performance and tuning. The higher one gets the less oxygen there is the less efficient and lower power and lower fuel economy will be unless they are specifically tuned for a set elevation. I think one is good from sea level to around 3-4K feet anything over that will be very noticable.