What is wrong with my plugs?

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This topic contains 20 replies, has 7 voices, and was last updated by Avatar PugetSoundBoater 2 months ago.

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  • john8504
    john8504

    Replies: 139
    Topics: 23
    #173132

    15 hp sears/ted Williams 15hp w/ tecumseh engine.
    Been battling this motor for a while. New stator, super clean carb, new plugs, new impeller, new fuel pump.
    I changed plugs again today because I’m trying to get rid of a sneeze at wide open throttle. It doesn’t sneeze at low rpms.
    I take the boat out for a couple hours of fishing and it seems to be running good for the 2 minutes it takes me to get to my first spot. Fish for 2-3 hours and I head to next spot. At wot, it sneezed 6-7 times in quick succession and seemed to bog down. *this is new*
    I turn and head back to the dock. Plane out at wot and it’s ok for about 1 minute and it slowly starts losing power. I have to idle for a couple seconds and then I can go wot again. This happened 2-3 times.

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    garry-in-tampa
    Lifetime Member
    Replies: 3065
    Topics: 29
    #173134

    The top plug looks like it’s not getting enough fuel – the other, too much. A blown head gasket would show up with a compression check. I cat’t say much more as I am not familiar with that motor . . .

    john8504
    john8504

    Replies: 139
    Topics: 23
    #173137

    No leaks from the motor that I can see. When I replaced the stator, the top seal seemed to be fine. I’ve never had to take the powerhead off so not sure about bottom oil seal. I’ll do a compression check tomorrow.

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    dave-bernard
    US Member - 2 Years
    Replies: 845
    Topics: 10
    #173140

    poor fuel flow from the tank to carb ???? check filter in tank. and motor.

    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4037
    Topics: 416
    #173143

    You didn’t mention anything about the spark plug wires so it might be worth checking the spring connector inside the boot for corrosion and the wire itself for continuity with a multimeter. It’s amazing how much trouble a bad connection in the boot can cause. As for spark plugs, try a set of NGK’s. You’ll be glad you did.

    Slowing down after planing for a minute and then catching its breath after idling for a bit sounds like a fuel delivery problem or possible overheating issue. With a new fuel pump, it could be sucking air in at the hose connectors either at the tank or the motor end. If the connector looks like this one, it can be taken apart and a new O ring installed.

    • This reply was modified 2 months ago by Mumbles Mumbles.
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    billw
    US Member - 1 Year
    Replies: 1019
    Topics: 33
    #173157

    Top plug looks like it might be loosing spark and getting WASHED with fuel it can’t burn. That’s my guess, anyway. You say you have replaced the stator. I am not familiar with this particular motor, either. Does it have separate ignition coils? Can you swap them and see if the problem plug changes to the bottom one? I would also check for overheat, like Mumbles said, just to be safe. When you say “looses power,” ignition would be rather instantaneous or on-off in nature; whereas overheat would be a gradual drop off.

    john8504
    john8504

    Replies: 139
    Topics: 23
    #173160

    Mumbles:
    I have tried pulling the wire out of the coil to replace them (just because) and have had no luck. I can’t find any information on these to know for sure that this part is replaceable without replacing entire coil. As far as the connector, it’s a quick connect style. The same style you have you hose to your air compressor. When I got the motor it had a Walbro style plastic external pump that was leaking so I replaced it with another one. They are all lawn mower pumps if I’m not mistaken.

    Billw:
    I will try and swap the coils and check my impeller. It’s peeing water fairly well so I don’t know how it could overheat while having circulation.

    john8504
    john8504

    Replies: 139
    Topics: 23
    #173161

    Here is a pic of the coil and the engine diagram from my manual.

    • This reply was modified 2 months ago by Mumbles Mumbles.
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    john8504
    john8504

    Replies: 139
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    #173164

    Also, compression is 114 on top cylinder and 110 on bottom cyl.

    Tubs
    Tubs
    US Member - 1 Year
    Replies: 2219
    Topics: 127
    #173171


    The fact that it will run when cold and then starts
    to fail as it gets warm could indicate a coil or
    condenser is failing. Picture of the magneto
    would be helpful.

    • This reply was modified 2 months ago by Tubs Tubs.
    john8504
    john8504

    Replies: 139
    Topics: 23
    #173179

    Pic of the new stator

    • This reply was modified 2 months ago by Mumbles Mumbles.
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    john8504
    john8504

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    #173278

    Checked spark on my coils. I backed it out 3/4” and I still have great spark. Bottom cylinder not burning off correctly. I would think that if the halves of the case were worn then both cylinders would be bad.

    Tubs
    Tubs
    US Member - 1 Year
    Replies: 2219
    Topics: 127
    #173316

    john8504
    john8504

    Replies: 139
    Topics: 23
    #173392

    Found my problem. It was the type of plug. Switched to some Ngk racing plugs and runs like a champ!!

    • This reply was modified 2 months ago by Mumbles Mumbles.
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    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4037
    Topics: 416
    #173395

    Switched to some Ngk racing plugs and runs like a champ!!

    What did I tell you! 👍

    I’m not sure what you mean by ‘racing’ plugs but I feel off the shelf NGK plugs are superior to anything currently on the market. Others may think different but I’m convinced.

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