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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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Working on a 1999 9.9 mercury 2 stroke. Removed and cleaned

Customer Question

Working on a 1999 9.9 mercury 2 stroke. Removed and cleaned carb, install gasket kit. Solved the stalling issue I believe was related to the fuel pump. It starts fine and does not stall but has an occasional misfire? coughs? when at idle or when accelerated.
Submitted: 5 months ago.
Category: Boat
Expert:  Tan replied 5 months ago.

Hello. My name is Tan.

What was your initial setting for the idle jet?

The only way to find a misfire is with the use of a timing light. Connect the timing light to the top cylinder run the engine till it misfires while watching the fl;ash of the timing light. The light should have a steady flash with no dead spots. If you see any dead spots move the ignition coil of the misfire to the other cylinder. Now test again did misfire move to the other cylinder or stay?

Customer: replied 5 months ago.
Manual said 13/8 to 11/2 turns out.
Expert:  Tan replied 5 months ago.

Ok that is correct. That is just the initial setting then when in the water and warmed up fine tune the adjustment to get the best idle. Which sounds like you have already done. That leaves the timing light test for a misfire.

Do you have a timing light to do this test?

Customer: replied 5 months ago.
no timing light just part testers. Its a very inconsistent sputter.
Customer: replied 5 months ago.
spark testers not part testers sorry
Expert:  Tan replied 5 months ago.

Is the spark inconsistent on both cylinders?

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