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Mercury 1985 18hp Outboard

M

mltrade

New member
Hi Guys - newbie here. Stuck on an issue with a 1985 18HP outboard. It's electric start, long shaft. S/N is 6205431. I've recently done a carb kit, new fuel fliter, new plugs. Engine starts and idles OK, and runs fine at high RPM submerged in a bucket in the yard or with ears. I'm getting good flow from the water pump (or at least it's pissing strong so I think it's ok). The issue is when it's in the water and the boat's underway. I have to pump the ball on the gas line every 15 seconds or so to keep the engine going, or it just stalls. I have to pump it less frequently at idle speed or lower RPM, however it will still stall eventually if I don't. I've replaced the ball pump on the gas line thinking that was the issue, but still the same. And I've tried adjusting the mixture screw on the carb while I'm out on the water, but doesn't seem to fix the issue. Any help would be greatly appreciated!
 
Re: Mercury 18hp Outboard

Do not run the motor at high RPMs out of the water. You are inviting a disaster. Rebuild your fuel pump. Then make the final carb adjustments with the motor in water and in gear.
 
Re: Mercury 18hp Outboard

I'll bet you a six pack that you have the wrong carb to block gasket (or it's upside down). There's a hole there where pulses come through to operate the fuel pump. If not that, then you have the gasket stack for the pump assembled wrong.

Jeff
 
Re: Mercury 18hp Outboard

Thanks guys, I'm going to order another carb kit and try again. Not surprised at all to hear that I have something in the wrong spot!
 
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