Discussion in 'Outboard Maintenance' started by Un-shore, Mar 24, 2010.

  1. Un-shore

    Un-shore Well-Known Member

    Okay, I've been around boats long enough to know that anything is possible but this is wierd.

    A couple weeks ago I was test running my merc 9.9 after it sat a while. It ran really rough and I could hear snapping sounds. I found that the coil casings were cracked and the charge was grounding to the block.

    Just for kicks I took off the coils and filled the cracks and coated the coils with epoxy. When I put the coils back on the motor ran just as bad but smoked a lot. Bad gas maybe?

    I cleaned my tank and put new gas in it and ran the motor to run the bad gas out of the block. Still ran like smack and oil just dribbled out of the exhaust like one of the cylinders wasn't firing.

    Checked the spark and it was strong on both cylinders.I tried running it again and still rough.

    Pulled the plugs and they looked good but I cleaned them and still ran the same.

    I thought I should check the plugs by grounding them to the block just to see if the spark tester was lying to me.

    There is this nice flat bare spot between the coils that the spark plug fits in perfectly and one of the wires to the coil held the plug in place like this spot was designed for what I'm doing. I pulled the cord on the first plug get a nice sweet snapping spark. I tried the next plug and get a nice spark too but this time the motor fires up and starts running, and better than before with that plug in. Oops! I flip the kill switch and figure there is something wrong with that cylinder.

    I put the plug back in and started to wrap up when I thought just one more pull to see if anything feels broken or loose. I pull the cord and the motor fires up like it's brand new and idles right along!

    I run and flip on the water and scramble to the shed to get the gas tank and it is still idling along as I hook up the tank. Now it runs perfect!

    What the heck just happened? :-?

    Something else that was strange to me was when before all this I was checking the coils with an ohm meter every contact point I checked to ground had continuity. Even the spark plug lead, I would think that would be the last place you would have continuity to the block? Maybe when it's running it might be different.
  2. Brett

    Brett > PRO STAFF <

    Might be a good day to buy a lotto ticket or two... :cool:

    Testing coils you're looking for a specific resistance value.

  3. firecat1981

    firecat1981 BBA Counselor

    Not sure if this is the answer, but I had a similar experience once with a car.
    I had an 86 mazda rx-7, as most know it had a rotary engine in it that works more like a 2-stroke then a 4. Well I let it sit for a few weeks after a hurricane where it was flooded out, I had tried starting it but it didn't want to fire up that day. After a few weeks I tried working on it again, it would start but ran very rough and had no power. I had spark, I had fuel, but still it wasn't right.
    Well I pulled the plugs on one rotor and fired it up, it ran slightly better on the single cylinder. I put the plugs back in and tried it again, this time it ran perfect. I noticed that from the plug holes oil had spewed out and was dripping down the block.
    So the only think I can conclude from my issue was the rotor chamber was flooded with to much oil and wouldn't fire, after blowing it out of the spark plug holes and probably into the exhaust it cleared enough to fire again.
  4. hoser3

    hoser3 Well-Known Member

    I would replace the coils. My guess is that you have a short in one of them and the problem will return while you are on the water after the engine heats up. :'( :'( :'(
  5. Un-shore

    Un-shore Well-Known Member

    Firecat, now that you mention it that does sound logical. I saw some oil as I was putting the plugs back in but it was dark out and I didn't think there was that much, but who knows what I didn't see in the dark.

    Hooker, I was wondering the same thing so I was thinking about a test ride when I get a new trolling battery just because I'm curious if the epoxy works.