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70 HP Merc problem

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Paul Aiken

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" I have a "79" Mercu

" I have a "79" Mercury 3 cyl 70 hp that is in excellent condition. Fresh water all it's life.
My problem is after taking off and coming up to speed in about 10 minutes it will start to bog down as if it is running on 1 cylinder. The local dealer has had it 3 times(so far!) The plugs were changed, and I was told the gas tank cap vent was probably not venting enough. After trying again with the cap off, the problem remained. Next they said it must be the carb's, so they were rebuilt.....no luck still the same! I lost all of last summer's fishing! Now they suspect something electrical; coil, etc..
Anyone have any similar problems? My engine will run perfect hooked up to the flush fitting, and for about 10-15 minutes after first launching. It seems after it warms up is when the problem starts. "
 
" Paul, it sounds like you mig

" Paul, it sounds like you might have an electrical problem. From your description, I would ck out the stator. I have replace quite a few of them that have your symtoms. The thing to do would be to ck the resistance on the stator leads (disconnected from the switchbox) when the engine is cold. Then run the engine and when it cuts out ck them again, shoud be a dramatic change if it is bad. Get a plastic 55 gallon barrel, put the engine in it, fill it with water, then run the engine in gear at idle (keep the water hose running in the barrel), it should develop the problem after about 20 minutes. "
 
" Paul,

One thing I would a


" Paul,

One thing I would add to Daren's comments is that it might pay to check your fuel pump. A pin hole in a diaphragm or a malfunctioning valve can cause similar problems to what you describe.

Tony "
 
" I have a 78' 85HP Johnso

" I have a 78' 85HP Johnson that does a similar thing, it runs great for the first 10-15 min, then when running at Idle it will die and then will not start until it cools down, I have not yet found the solution to it. I think it is electrical, but not for sure. "
 
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