Please help!

Discussion in 'Bubba's Outboards' started by droptine77, Jun 1, 2008.

  1. droptine77

    droptine77 New Member

    Messages:
    469
    State:
    Anderson, SC
    Did Johnson make low compression motors? I have been told to check the compression on motors before I bought one and in the last two days I have look at two 70hp johnsons from the mid 70s and both had around 50 psi oneach cylinder. Is this normal or are both wore out engines?
     
  2. swampratt

    swampratt Member

    Messages:
    217
    State:
    oklahoma
    my 90 johnson v4 year 1983 had 135psi on 3 cylinders and 35 on 1...Newer mercs at least the one of my cousins was 95 psi on all cylinders. we thought that was low but it was brand new and runs great....

    If a regular engine, like a car engine has a low cranking pressure cylinder...Then that plug will usually (just about always) look like it is running rich ..

    It will be all black and sooty..even after short runs