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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4726
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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I just purchased a 1989 Grumman with a 40 Horse Merc

Customer Question

hi Jeff. I just purchased a 1989 Grumman with a 40 Horse Merc Classic. The first time I took it out I had difficulties getting the engine to start. Once the engine started and warmed up it ran seemingly perfect. The water pump seems to be pumping water good. The next day I took the boat out and the same difficulties getting the engine started. After getting the engine started it seemed to run fine at idle speed. When I opened the the throttle to full the boat moved at half speed at best. I pulled the cover off and noticed fuel leaking from the upper carb and the fuel that was leaking is getting water in it. The carb seems to be leaking from the bowl gasket. obviously I need to get a new gasket for the carb but what would be causing the water getting in the fuel? I did not notice the water in the fuel the previous day when the boat was running at full speed and idled good. The engine does not seem to be missing and now that this issue has occurred it will not stay running at idle.
Submitted: 1 year ago.
Category: Boat
Expert:  Jeff G. replied 1 year ago.

The water is coming from your fuel tank. There is no place on the engine where water and fuel mix. Some larger engines have water cooled fuel, but not yours. Remove the fuel line going to the engine. Get a glass jar and using the primer bulb fill the jar about 1/2 way with fuel. Let it sit for a little bit and check to see if the water separates from the fuel.

If any water, drain the fuel tank, clean it out and put fresh fuel in. Is it a portable tank?

If a vent was open and the tank exposed and you had rain it could get in that way. But I would guess it was already in the tank from condensation or maybe some bad fuel. It was just mixed in previously.

Drain the carbs as well into some paper towels, then once you have filled the tank with fresh fuel and the carb drains still open squeeze the primer bulb to clean all the bad fuel out of the engine, then close the float bowl drains and start the engine. Make sure you clean up any spilled fuel.

post back ny questions and what tank you have.


Customer: replied 1 year ago.
Thanks! I took the boat out today. I replaced the fuel filter and put a new gasket on the upper carb. However I think possibly the prime bulb is bad. I had to have someone pump it lightly to get up to full throttle. Could it be just that or would the fuel pump keep the engine from keep fuel to the carbs?
Expert:  Jeff G. replied 1 year ago.

If pumping the primer bulb helps keep the engine running then look for either an air leak at a fitting or a weak, failing fuel pump. I would be leaning towards a weak fuel pump not keeping the carbs full.

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