1996 40 hp merc intermittent high idle

M

mtrice

Cadet
Joined
Apr 12, 2010
Messages
7
I have a 1996 Mercury 40hp 4 cylinder. Have owned for nearly 6 months and has ran great.
Put new throttle cable on 2 months ago, everything has been fine. Last time I was out, after about 3 hours it started idling high by itself, out of the blue. Stopped shortly after and seemed fine. Today, after about 3 hours it did the same thing, idling very high by itself, and when I went to give it more (full) throttle it just spit and spattered. Any idea where to begin looking for cause? Checked all cylinders and have good compression in each. Thanks in advance for your response to my inquiry.
 
D

donzi gt230

Petty Officer 3rd Class
Joined
Jul 19, 2010
Messages
92
Re: 1996 40 hp merc intermittent high idle

I would guess it's a fuel delivery issue of some sort, running lean. Check hoses, tank vent, pump, etc. If you take it back out and it starts high idling try pumping the fuel bulb and see if it changes.
 
M

mtrice

Cadet
Joined
Apr 12, 2010
Messages
7
Re: 1996 40 hp merc intermittent high idle

Thanks so much for your response. Thought crossed my mind it may be something fuel related. I think I forgot to mention that I was crabbing, and boat was running at preety much and idle for nearly 3 hours-not good, right? Seemed to run fine on muffs when I got home. Today got home and noticed fluid slowly leaking from prop shaft. After reading some other threads I understand possiblity unburnt fuel/oil? Does this sound right or should I be looking for something else now with lower unit?
Thanks,
 
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