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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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I have a 50hp mercury engine, 1984 model. after getting the

Resolved Question:

I have a 50hp mercury engine, 1984 model. after getting the boat up on plane and running couple 100 yards it starts to stall then wide open again, stall-then good. this will continue until i let off the throttle. Sometimes when throttling up to get on plane it will do this until the stalls and on again gets closer together until it does run ok. Any help would be appreciated. A friend thinks it is the power pack.
Submitted: 8 years ago.
Category: Boat
Expert:  Dominick replied 8 years ago.
Thank You For Your QuestionCustomer

The first thing we need to do is determine where the problem is...My experience tells me that you are starving the engine for fuel...What I mean is, when the engine dies down it needs less fuel so it "surges" to a higher power, when at this higher power the fuel is not being delivered fast enough and the engine dies back down to a lower power output, and this cycle repeats itself over and over...

We need to do a compression and ignition test just to get that out of the way, (I don't think you will find any problem with either one of these, but it is the prudent thing to do...

If we skip that step, lets go straight to the fuel delivery. I have found it best to replace the fuel tank with a carry on tank of known good quality...Run the engine again and see if the problem goes away. If the engine runs fine, the tank pickup is plugged, the primer bulb is bad, one of the connections is causing a restriction or some other part of the fuel system in the boat is causing your restriction of fuel. If the problem remains the same, the problem is on the engine. These will include the engine fuel line connection, engine filter, fuel pump or the carburetors. You can try squeezing the primer bulb when the engine is surging, If this remedies the problem, the fuel pump is most likely the issue.

When you do the fuel tank test, I am sure you will be pointed to the right component...

I believe we will find the problem most likely the pick tube in the tank, primer bulb, fuel line connector restriction or air leak.
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