Motor compression

Discussion in 'Bubba's Outboards' started by edward361, Jan 30, 2007.

  1. edward361

    edward361 New Member

    Messages:
    117
    State:
    Shiner Tex
    I have a 1986 Johnson 150 GT. what compresion for should i be looking for in each cylinder.thank you
     
  2. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
    The main thing is that all cylinders have close to the same compression. If you have like 85 89 and 45 on other cylinder then you have to worry. Compression should be around 80-100 id say depending on engine wear. As long as all cylinders has close to the same then your OK. I'm sure someone else knows what psi the cylinders "should" have.
     

  3. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Around 110 to 120 would be great. 100 would run any thing below that would make it hard to start but would still run. If it rope start about 70 to 80 will be about all you can pull out of it.

    As said above they need to be wintin 10 to 15% of each other. A 120 on one and 80 on another says you have a serious problem on the low cylinder.
    Hope I didn't cornfuse you here, Heck I think I may have cornfused myself a little.:lol:
     
  4. edward361

    edward361 New Member

    Messages:
    117
    State:
    Shiner Tex
    I have
    1. 96
    2.96
    3.96
    4.85
    5.90
    6.94
    The factory said 105 new do you think i've got a problem with #4.
     
  5. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    I would do a decarb and then recheck them paying close attention to number 4. I would use seafoam and soak each cylinder about an hour then follow the decarb instructions. The rings might be coaked up some.
     
  6. edward361

    edward361 New Member

    Messages:
    117
    State:
    Shiner Tex
    Thank you Bubbakat I did the Decarb @ soaked the cylinders with seafoam now Ihave got
    1 101
    2101
    3 100
    4 98
    5101
    6 100


    THANK YOU VERY MUCH
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Thanks for the follow up edward. Now when you mix your fuel always add 2 or 3 ounces of seafoam to every six gals of gas and it will keep those rings free.

    If you troll a lot with that big ole six try gaping those plugs at 40 and it should help with the coaking problem.