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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3721
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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2004 Mercury 125 hp saltwater series. Stalls at idle.

Customer Question

2004 Mercury 125 hp saltwater series. Stalls at idle. Changed the plugs, now it does not stall but revs slowly up to appx. 1800 rpm then suddenly drops to idle as if a kill switch was activated momentarily. Then it repeats the idle up and drop cycle again and again, slow and steady. Its impossible to dock like this.
Submitted: 11 months ago.
Category: Boat
Expert:  Charles replied 11 months ago.

Hello, my name is***** will assist you.

Expert:  Charles replied 11 months ago.

What this is sounding like is that you have either the #3 or #4 carb flooding slightly and bringing the RPM up some. When the fuel runs out, the idle will drop back down to normal. This engine does not idle on the bottom 2 cylinders, they are activated by a booster pump in the throttle linkage and really only are supposed to come in around 1800 - 2000 RPM.

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