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Dominick
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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On a 1989 90 hp Mercury outboard engine, serial # *****

Customer Question

On a 1989 90 hp Mercury outboard engine, serial # ***** there are two adjustments on each carburetor, the one on the right side I guess is the fuel air adjustment. The needle on the top of the carb, left side is just an air needle adjustment. How do I properly adjust these carbs
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.
Hello my name is ***** ***** am I speaking with?
Click this link to pull up a diagram. Do your carbs look like this?
https://xfer.mercmarine.com/pximages/partscatalog/Common//15158_500.gif
Customer: replied 1 year ago.
Yes
Customer: replied 1 year ago.
As far as I know the jet number 25 on dia. Is turned out 1 1/2 turns. The jet number 28 I have turned all the way in, don't know where that one should be
Customer: replied 1 year ago.
My name is Ed
Expert:  Jason replied 1 year ago.
Hi Ed..... Lets see here...... Did you remove #28 form the carbs?
Expert:  Jason replied 1 year ago.
Hi Ed, i'm going to decline the all.
Expert:  Jason replied 1 year ago.
You removed or otherwised touched that screw, correct?
Customer: replied 1 year ago.
Yes I did
Expert:  Jason replied 1 year ago.
You were not supposed to. The reason I declined the call is because this isn't something I'm going to be able to help you with here. You are going to have to take the engine to somebody that knows how to tune carbs by ear. Which means you need a master mechanic. That screw is pre-set by the factory and it is not to be touched. And there are no instructions or specification for that screw. It has to be done by ear/feel. I'll add a picture for you. You can give that a look. Sorry I can't help you with this one.

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