rejetting for altitude

[fish lake man]

I have a 1997 mercury 15hp two-stroke boat motor. It is jetted for sea level. I now only fish at approximately 9000 feet. I have changed the prop, but still have some bogging. Would like to rejet. Can anyone tell me how to remove the jet? Thanks

 

[Fuzzytbay]

Re: rejetting for altitude

There's fish at 9000 feet?.... remind me to pack my fishing rod next time I get on a plane.......J/k
I have no idea how to change your jet, but yes it needs to be changed.
Just out of curiosity, where is that lake?

 

[fishrdan]

Re: rejetting for altitude

I assume you're talking about Fish Lake Utah.

I'm not any help on the Merc outboard as I've never dug into one, but you need to swap out the main jet, that should be it. I've had 2 different engine's I've tuned for that elevation and you are going to need to jet down about .004 to .005. (IE; if your main jet is a 55 go to a 46 or 47) my I/O had 60 mains and I went with 55's. I didn't have to change/adjust anything else, just swapped out the main jet(s). Oh yeah, I did swap props like you have all ready done.

Go to crowleymarine.com and look up your outboard in their parts catalog, it should give you some indication of how to get to the main jet and what P/N to order for the proper high altitude jet. On my Force outboard I have to remove the carb and drop the bowl to gain access to the main jet, pretty simple 30 minute job.

Hope that helps,,, even though it didn't answer your question.

 

["G"]

Re: rejetting for altitude

Re jetting is simple.. knowing what to re jet to is not. Merc puts this info into their manuals I think... Look into it and perhaps your friendly mechanic can help at your elevation.

I used to have those specs but that was YEARS ago... didn't think I'd ever need them. Go figure! Look for sizes of the jets as some have spoken to already... They only make sizes for altitude changes of 5000' and above as I recall. Where you fit in that notion may be two sizes down.

Specs are what you need, not my memory... Be careful that you don't lean yourself out too far!

"G"

 

[no704]

Re: rejetting for altitude

May not apply, but when I used to drive my VW bus at high altitudes it was alot happier running a lower octane fuel.

 

[199675hpforce]

Re: rejetting for altitude

I rejetted my outboard but wished i had not. If yours is premix system just leave it alone. The rejet would make the orfice smaller, which also means less gas and oil. You also are always better off richer than leaner with 2 strokes.