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1995 Merc 60hp low RPM

J

jimdorn

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" At full throttle, the engine

" At full throttle, the engine only produces 2800-3200 RPM. It runs smooth and doesn't appear to be missing. The problem started as an intermittent thing. I checked the linkage and the carbs are opening all the way. Fuel pump and fuel filter are my next likely candidates. Anyone have any other ideas or suspects?? "
 
" Jimdorn,

I'm

" Jimdorn,

I'm just a hack, but here's my 2 cents.. Replacing old plugs is never a bad idea, but I think if there was bad spark on one cylinder, the engine will not run smoothly at any RPM. Checking for weak spark across the board wouldn't be a bad idea though.. Assuming the compression is good on all cylinders (over 100 and within 15 PSI), my #1 suspect would be fuel. A clogged carb, weak fuel pump, or restriction in the line would be what I would look for.

Jon "
 
" You can check for a carb pro

" You can check for a carb problem by using a squirt spray bottle of gas and spraying it into each carb while you have someone drive the boat for you. If the engine picks up, you know that you have found the carb needing attention. "
 
" Hi jim I have a 50hp. 1985 m

" Hi jim I have a 50hp. 1985 merc I just fixed a problem that sounds like yours, it was a blocked exhaust.I found it to be a problem caused by cheap oil. You have to pull the head off, and clean the exhaust out. there is no thermostat in my engine so now I use top quality oil only to cut down on deposits. Good Luck!!! "
 
I have the same motor and mine was doing that. I had the #3 coil out. Was only running on two cylinders but ran decent on the two. lol This how I tested mine.
Remove plug wire from spark plug.
Using a VOM on ohms scale (I used the 2K scale) measure from the ground lug of the coil to the end of the plug wire. It should read .900 to 1.000 or 900 ohms to 1000 ohms on an original factory coil. I bought two different brands of replacement coils they measure .495 or basically half of the original Mercury coil.
I was suspicious of the lower reading on the replacement so I ordered the second replacement (brand) and it also measured ~.490.
I tried the replacement coil and the #3 cylinder was firing ok. I had previously just pulled each plug wire one at a time and noticed no fire on #3.
After the coil replacement mine rev'd far beyond what it did before. I don't have a tach.
 
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