Elevation change question?

[7lazy77]

Just purchased a new pontoon boat in Nebraska & brought it home to Wyoming. The boat has a 1994 115 hp Johnson on a 24' pontoon. There is a difference of 6300' in elevation from where I picked it up at & where I live. Is there anything special I need to do to the motor to adjust to this new altitude? Is there a "rule of thumb" at a certain elevation change when I need to re-jet the carbs?

 

[Silverbullet555]

Re: Elevation change question?

I would think you will need to rejet and you will likely need to reprop the boat.

6300 feet in elevation increase means 35%+ decrease in HP and you will notice that and so will the boat. Smaller prop so it can get in the proper RPM range will be needed IMHO.

 

[wilde1j]

Re: Elevation change question?

High altitude jetting is covered in the OEM shop manual and is clearly needed at 6300' MSL. SB is also correct about the need for a lower prop pitch, since your motor will develop ~ 20% less HP [3.5% per 1000" altitude increase] (not 35%) at that altitude. Jets are typically available in at least two or three altitude bands. Again, all covered in detail in the shop manual. Any BRP dealer near that operating altitude will be completely familiar, since they routine change jets for sea level boats all the time.

 

[7lazy77]

Re: Elevation change question?

Any recommendation on prop size? We generally use the boat for fishing & occasional tubing.

 

[wilde1j]

Re: Elevation change question?

Lower pitch than what you currently have. A decent dealer could advise you as to how much pitch change you should make. BTW, what is current WOT RPM? Your motor should turn ~ 5800 @ WOT.

 

[7lazy77]

Re: Elevation change question?

Sorry for the dumb question, but what is WOT?

 

[wilde1j]

Re: Elevation change question?

Wide open throttle.