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Thread: Other outboard engine problems

  1. #1
    Member markopolo50's Avatar
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    Default Other outboard engine problems

    What am I doing wrong?? I have a Mercury 75hp outboard, 4 years old. Last fall it started stalling at idle. Ran pretty good above 1000rpm. So I thought the gas might be suspect. I ran it pretty much empty, put in Stabilizer. This spring I added some dry gas and filled up with fresh gas, 19 gal in 20 gal tank. ---- Same problem. I did drain the carbs, changed plugs and gas filter. What am I down to, pulling carbs and cleaning?? Any other options?? Am I doing something wrong?? Not my first outboard but my first 4 stroke outboard. Thanks, Mark

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    Member Tolman24's Avatar
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    It will be interesting to hear what the solution is. My guess would be a varnish build up on the idle path. I am not familiar with this specific engine.

    When I was running carbed 2 strokes years ago I was told by on old mechanic that if I pulled the fuel line and ran the carbs dry EVERY time I took the boat out of the water (trailer boat) that I would never see him again. He recommended using the electric choke when it started to sputter to get it all. I did this religiously and didn't need a carb job for almost 10 years. I only needed it then because the fuel lines deteriorated and got little pieces of rubber in the carbs. Now this was with older 2 strokes so it may not be the same with carbed 4 strokes. I do know that you should not do it with fuel injected as the fuel supplies lubrication.

    If I was in your shoes I would probably pull the carbs and clean them. Look for varnish in the idle path.

  3. #3
    Member markopolo50's Avatar
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    Default Carbs

    Quote Originally Posted by Tolman24 View Post
    It will be interesting to hear what the solution is. My guess would be a varnish build up on the idle path. I am not familiar with this specific engine.

    When I was running carbed 2 strokes years ago I was told by on old mechanic that if I pulled the fuel line and ran the carbs dry EVERY time I took the boat out of the water (trailer boat) that I would never see him again. He recommended using the electric choke when it started to sputter to get it all. I did this religiously and didn't need a carb job for almost 10 years. I only needed it then because the fuel lines deteriorated and got little pieces of rubber in the carbs. Now this was with older 2 strokes so it may not be the same with carbed 4 strokes. I do know that you should not do it with fuel injected as the fuel supplies lubrication.

    If I was in your shoes I would probably pull the carbs and clean them. Look for varnish in the idle path.
    Tolman, thanks for the reply. I was thinking along the same lines although the 4 carbs don't look too inviting. I believe that may be my only option though. Thanks, Mark

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    Default Carbs for sure

    I just had the same deal with a 1999 50hp 4stroke, kind of. At idle and at higher rpms, I would get a spit and sputter. This sometimes would be just short of stalling at idle. I did the same thing you did, fresh fuel and filters, plugs (tried to isolate which plug it might be), checked all fuel connections for air leaks, nothing. Well, off to someone who knows better who cleaned the carbs which he said were not that dirty and sycronized the carbs. $300 and I'm out the door with a motor that sounds new.

  5. #5

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    You could try a fuel system cleaner too before you get too carried away and dissasemble everything. They work on 4 strokes outboards just as they do in automobiles and trucks. I have had some idle issues with my sensitive Hondas in the past and carb/fuel injection cleaner did the trick to my surprise.

  6. #6
    Member markopolo50's Avatar
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    Default Carb cleaner?

    Quote Originally Posted by T.R. Bauer View Post
    You could try a fuel system cleaner too before you get too carried away and dissasemble everything. They work on 4 strokes outboards just as they do in automobiles and trucks. I have had some idle issues with my sensitive Hondas in the past and carb/fuel injection cleaner did the trick to my surprise.
    TR
    Any suggestion as the brand of fuel system cleaner? I have seen those but some claim more than others. Thanks for all the help, Mark PM sent

  7. #7
    Member markopolo50's Avatar
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    Default Carbs cleaned in outboard motor with Seafoam

    Well I have run about 15 gallons of "treated" gas through the outboard that wasn't idling. I first tried Gumout fuel system cleaner and didn't work so I added a can of Seafoam motor treatment and ran some more. I ran different speeds and tried to make it idle as the gas went through. It slowly got better and is almost 100% idling now. Thanks for the advise, Mark

  8. #8

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    Quote Originally Posted by markopolo50 View Post
    Well I have run about 15 gallons of "treated" gas through the outboard that wasn't idling. I first tried Gumout fuel system cleaner and didn't work so I added a can of Seafoam motor treatment and ran some more. I ran different speeds and tried to make it idle as the gas went through. It slowly got better and is almost 100% idling now. Thanks for the advise, Mark

    My C-Dory buddies praise the Seafoam treatment. Glad to hear you didn't have to tear everything apart See you on the water....

  9. #9
    Member breausaw's Avatar
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    I indorse Seafoam also, have heard you can run it directly into the carbs without causing damage and this may fix your problem: put a can in each tank in the spring and after each service. Only drain the carbs before mothballing in the fall canít see how you can get varnish buildup without evaporation. We take the boat out most weekends so carbs stay full, for me the jury is still out with respect to running the carbs dry after each trip.
    Just my thoughts, take it what its worth.
    Jay
    07 C-Dory 25 Cruiser
    OurPlayground.


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