How to adjust the air intake?

[youngboater]

Hi All,<br /> I was wondering if there was a screw or a way to simply adjust the fuel air mixture on my outboard or something. I know I'll always lose power at high elevations but anything will help. I'll be using it at about 8,000-9,000 feet above sea level (only a few times a year though). Mercury 75 HP 2-Stroke oil injection (2002). Anything is better than nothing. Thanks

 

[LubeDude]

Re: How to adjust the air intake?

The only way to make your engin run right at those elevations is to re-jet the carbs, Some where in the neighborhood of .002 per elevation above 2,500 feet. Anyway, that is what my Merc 150 recomends.<br /><br />So:<br /><br />2,500 + .002<br /><br />5,000 + .004<br /><br />7,500 + .006<br /><br />This is for all jets, Idle, high speed, and vent.

 

[youngboater]

Re: How to adjust the air intake?

Thanks LubeDude. I also have an (2004) 8 HP 2-stroke Mercury kicker, would this be the same fix as as the 75? Does anybody else know much about this??? Maybe a Simplier way??? Info Much Appreciated

 

[Chinewalker]

Re: How to adjust the air intake?

Hi Youngboater,<br /> Because of the age of your motors (practically new) I would highly recommend taking them to a dealer to make the changes, as anything you do may void the warranty or any extended service coverage you may have...<br />- Scott

 

[youngboater]

Re: How to adjust the air intake?

I will do just that Chinewalker. Thanks

 

[LubeDude]

Re: How to adjust the air intake?

Great idea to see your dealer firs, I should have suggested that also. It depends on the engine as to what jetting you choose. My Merc 150 actually has to have a smaller jet in the idle circuit to richen the mixture. All engines are different. I do believe you will have to rejet for that elevation difference though. Been wrong before.

 

[backdraft]

Re: How to adjust the air intake?

Youngboater, since I boat at 4500 to 7000 , I would recommend a prop change as the easiest way to run your motor. The jet change is at the least somewhat hard to pin down exactly, and you have to change it back to the original settings. A Prop with 2 to possibly 6 inches less pitch will work quite well. KEEP and eye on your tach though. just a suggestion. nevjb

 

[youngboater]

Re: How to adjust the air intake?

Thanks, I will consider all advice given.

 

[LubeDude]

Re: How to adjust the air intake?

This is a bit of a tough one. I ocationally will go to a lake that is 4,500 feet. The boats i have gone there with run like crap when Im there. Very slow to plane and slow WOT operation. Its not likely that I am going to go through all the trouble of changing jets back and forth for just this one or two trips a year. Therefore I purchased a cheap aluminum prop for when I go there. The engine is still going to run very rich, especially at 7.500 feet. If you are planning to do any trolling I can guarantee you that you will have bad fouling issues, therefor you might want to rejet the small motor. Probably only one carb so not a big deal. Most jets can be changed without removing the carb.