Welcome Guest - Sign Up today
Welcome Guest - Sign Up today

Announcement

Collapse

Help Tip: If you have a question that has not been answered to your satisfaction in the archives, it is always best to start a new thread of your own. By starting your own thread, you will receive the maximum number of views by forum members.

Please note this topic has been inactive for 90 days. For the best results, please start a new topic.

Thank you all in advance for doing your part in helping iboats run a smooth ship.

Additional forum rules linked below.
http://forums.iboats.com/forum-rules-guidelines-405/
See more
See less

70 HP Johnson compression test

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • 70 HP Johnson compression test

    Just did a compression test on a 70 HP Johnson I picked up with a 16'
    what is a good number? i got 85 psi on top and mid & bottom was 70psi
    the motor is a '89 are these average for the year or should I be looking at new rings?

  • #2
    Re: 70 HP Johnson compression test

    I have a mid 80's 70 hp evinrude here. Compression is about 125 psi on each. As far as I have ever known (some may disagree, but I have always followed) once you get below 100 psi your getting border line on whether or not the motor is gonna run much longer.

    Comment


    • #3
      Re: 70 HP Johnson compression test

      Are you doing it with a pull rope or starter? It's low if your doing by a starter, and they should all be within 10% of each other. There really is no magic number for compression. Certainly if your above 100 your good but it is more important that the numbers are within range of each other. Read the "Top secret" file at the top of the Johnson forum and do a decarb and then retest.
      The Crestliner Restoration

      http://forums.iboats.com/showthread....49#post2218249

      1967 16' Crestliner and 60hp Johnny

      Klamath Trailorboat and 9.9 Johnny

      Comment


      • #4
        Sign up today
        Re: 70 HP Johnson compression test

        Appreciate the advice, just checked the 'secret file' useful info. I didn't warm up at all, just cranked it over with guage in. I think a retry with warm engine is in order. Thanks again

        Comment

        Working...
        X