40 hp mariner pops & spits

Discussion in 'Bubba's Outboards' started by turtle, Sep 25, 2006.

  1. turtle

    turtle New Member

    Messages:
    27
    State:
    Mo
    I have a 40 hp mariner that runs rough at idle it pops and spits back sometimes killing the engine.it stops doing it after it warms up but at full throttle it feels like something is holding it back.checked the plugs the porcelain is light tan but all around it is sooty and oily .it has a cdi unit not points any suggestions
     
  2. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Try choking it quickly at full throttle. If it picks up, you need the carbs done.

    Probably need them done because of the idle anyway, and get that gas checked for water.

    It's always good to be sure your compression is good and from what your saying about the spark plugs, you've got fire to them.
     

  3. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Do a compression ck and post it along with the year of that motor,

    I need to look ans see just what we are looking at here. It sounds like a low idle miss or as the old folks, say lean pop.
    Could be in the carbs or the fireing either one. The compression numbers will help some.
     
  4. turtle

    turtle New Member

    Messages:
    27
    State:
    Mo
    Thanks for the info guys. how much compression should it have and do you think i might try 1 step colder plugs.its a 85 or 86 mariner
     
  5. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    It looks like Bubba and I were on the same page last night.

    Don't change the heat range of the spark plugs.

    Compression should be in the 100# range, with not much more than a 10# difference between cyl's.

    After getting it running better, an engine of that age should get a decarboning treatment also.

    C'mon Bubba, your turn:lol:
     
  6. turtle

    turtle New Member

    Messages:
    27
    State:
    Mo
    Thanks for the info. i will check the compression as soon as i can also is there any thing i can get at napa or oriellys that would work to decarbon the pistons
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Sea foam makes a product for that and its called Deep Creep, comes in a air sol can and you use it just like it says. Get the engine warm and spray it into the carb until it chokes it down and let it die. Take the plugs out and tilt the motor up and spray the plug holes full. Let it set over night or an hour will do a lot for it and then take it out and run it for about an hour like you just stole it and was trying to get away.

    Shut it off and let it cool down somewhat and do the plugs again and let set 15 min and then take it out and run it hared for a few min. It should take care of the carbon.
    Then use sea foam in the fuel tank for a stabilizer and carbon cleaner.