Lower cylinder on evinrude 25 carbons up

Discussion in 'Bubba's Outboards' started by NascarBuckeye, Oct 19, 2009.

  1. NascarBuckeye

    NascarBuckeye New Member

    Messages:
    16
    State:
    Grove City, Oh
    I recently acquired a 1984 Evinrude 25 for what I thought was a great low price. But it needed lots of work as it had set for many years. After lots of repair I go to fire it up and it starts right up, but after running for a minute or 2 the motor starts smoking badly and then wont take fuel and slowly dies. I pull the plugs and the lower plug is carboned up badly. Its just black and dry. I put new plugs in it gapped at .030 and the same thing happens. I cleaned the new plugs then switched the coils thinking 1 has weak spark, but the lower 1 carbons up again.

    After I bought it I replaced all the fuel lines as they were very rotted from setting. I rebuilt the fuel pump. I cleaned and rebuilt the carb. I replaced the thermostat which was frozen closed. Of course I changed the impeller and lower unit oil as well. I checked the compression and both cylinders are at 124.

    Any ideas as to what might cause this lower cylinder to carbon up like this?

    Thanks,


    1984 Evinrude 25
    E25TECRD
    E0363767
     
  2. Iowa_Josh

    Iowa_Josh New Member

    Messages:
    1,463
    State:
    Central Iowa
    GO get a spark tester with an adjustable gap and test both. The one that fires should look dry. It shouldn't look wet if it's running?
     

  3. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Try decarb on the cylinder. Squirt it full of seafoam and put it in a barrel and let the cylinders soak for about an hour. Re gap the plug to 35 and use a QL77J4 champion plug and then run it at about 12 hundred rpm's. After doing this a couple times clean both plugs get a tank with one gal of fuel mix oil and sea foam in it take it to the water on the boat and run it like you stole it until the fuel is gone.
    Then remove the plugs and put in regular mix and it should idle and run okat then unless it has a bad coil or a broke reed valve. which by the way wouldn't have anything to do with the carbon.
    That lower cylinder is plum full of carbon or you have the oil and fuel mixed to thick. 50:1 will be the mix and I figure you already know that.
     
  4. NascarBuckeye

    NascarBuckeye New Member

    Messages:
    16
    State:
    Grove City, Oh
    After I switched coils I thought if the bottom coil was bad the carboning would move to the top cylinder. But then it popped in my head if it was a weak coil there should be wet fuel on the plug like its not burning off and flooding out. Instead it was dry carbon. I was thinking maybe a reed valve or the power pack was going bad but didn't want to throw money at it and did not know what problems those 2 would cause.

    What Bubbakat says make sense to me and I will try that. I do run 50:1 and always mix 1 gallon with 1 ounce seafoam as well which might cause some of the smoke if the carbon is built up in there.

    I found L77JC4 which I have a new set of. And I saw where I could order QL77JC4. Any idea what the difference is between these and QL77J4?

    Thanks for the answers. I'll let you know if the decarbing cleans out the cylinder.
     
  5. Salthart

    Salthart New Member

    Messages:
    1,264
    State:
    North Carolina
    First of all, Run a compression test and make sure both cylinders a pretty well equil. If they check out then remove the carb and spray some carb cleaner (Advance or Autozone brands work fine) through the reed block so that it goes into the crankcase of the lower cylinder. 5-10 seconds should be enough. Sometimes when an engine sits fuel bleeds into the crank case and the fuel will evaporate leaving the oil to get more and more gummyy. While you have the carb off may as well double check the float level and make sure the inlet needle don't have trash in it. (I notice you didn't replace the fuel lines and they can rot from the inside out letting tiny bits move on to the needle)
    My guess is a heavy float and/or jets set to rich. If I'm right in thinking this is a 2 cylinder, single carb engine, Then any richness picks on the lower cylinder.
    Let us know how it turns out.
     
  6. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Sam mix that seafoam heavy. A whole can will decarb her real good. The ql and the plain l is that the q is a noise resistance plug that will give you less interferance to you fishfinder both plugs are the same heat wise and will work.

    I would also pick up a can of deep creep also made by seafoam and spray it into the carbs and do it until it chokes it all the way down and that will clean the reed valves. You can put some seafoam in a squirt bottle and get the same results
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill




    Marty read his first post

    After I bought it I replaced all the fuel lines as they were very rotted from setting. I rebuilt the fuel pump. I cleaned and rebuilt the carb. I replaced the thermostat which was frozen closed. Of course I changed the impeller and lower unit oil as well. I checked the compression and both cylinders are at 124.

     
  8. Salthart

    Salthart New Member

    Messages:
    1,264
    State:
    North Carolina
    My bad, I just missed him saying the fuel lines being replaced.
     
  9. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Not a problem I have been guilty of that myself. In real life my wife calles it selective hearing and on here I call it selective reading.:smile2: