Force 75-hp jet question

[cloumar]

My 1998 - 75-HP Force runs not too bad when I use it in the area where I live which is about at 300 feet above sea level... and when I say not too bad I mean that in cooler temp like spring or fales it will be good and smooth accelleration and smooth running at cruising speed.

But when weather gets warm and humid like end of June and July it runs rougher and acceleration is not smooth and strong or if I go fishing out of town in region around 800 to 1000 feet above sea level it will be worst. So last year I made a test I installed a main jet one size leaner which is for the 1500 to 3000 feet range, the original was for the 0 to 1500 feet, and it made a hell of a difference, acceleration better - runs smoother at cruising speed.

The engine is OK all the way - carb clean and well adjusted - timing OK - compression OK - fuel pump OK rebuilt from last year - decarb OK - fuel is 89 octane - plugs NGK-BHW flat surface.

Do you believe I could leave that main jet which is only one size smaller (leaner) in all time ?


Thanks for help.

Mario

 

[steelespike]

Re: Force 75-hp jet question

I'm pretty sure your motor is designed to run best on 87 octane.I think most reccomend conventional plugs for normal operation.
Watch the plugs real close for any indication of running too lean.

 

[cloumar]

Re: Force 75-hp jet question

Hi Steelespike,

The plug I am running with are the one suggested by Merc dealer, for the gas till last yeat I was using 87 regular gas and it was not running better.

For the plugs they are often wet with black combustion deposit (oil-fuel) they don't show signs of lean now.

Thanks for the reply.

Mario

 

[steelespike]

Re: Force 75-hp jet question

The 89 is a waste of money unless specified in the manual.
If the motor is properly tuned etc. it is actually harder to burn the higher octane.While you have solved your problem with jets I think the cause is still present.
It's not normal for it to run on jets meant for a higher altitude.
There is a post here somewhere about fouling plugs they changed to the conventional plugs and solved the problem.Don't remember if it was a Chrysler/Force or what.
I guess if I was in your position I would be tempted to continue running it as is but might give conventional plugs a try.