1977 Johnson

Discussion in 'Outboard Maintenance' started by rstevens, Mar 22, 2010.

  1. rstevens

    rstevens I Love microskiff.com!

    So I have a 1977 70 HP Johnson and don’t know a lot about outboards. My question is where should water be coming out to cool the motor. The only spot that water is coming out of is at the bottom end, on the other side of the prop. I though that there should be some coming out up top somewhere? If so what’s wrong? And what do I need to fix?
  2. DuckNut

    DuckNut Brandon, FL

    Super Brett will rescue you...

  3. Tom_C

    Tom_C Well-Known Member

    Iboat Forum is the best place I have found for motor help.


    Post your ??? under the Johnson & Evinrude Outboards section.
  4. Un-shore

    Un-shore Well-Known Member

    Here is a link to a post with a similar question and will help.

    WARNING Some Adult Content! ::)

  5. Frank_Sebastian

    Frank_Sebastian Well-Known Member

    Change the thermostats and impeller every 2 years minimum. Also these motors have 3 carbs. If there is a noticable loss of power you must make sure it isn't a carburetor clogging up. If no gas is entering the cylinder then no oil is either.

    You can check this with it at idle on a hose. While at idle you can pass a propane torch (UNLIT OF COURSE) if front of each carb. If there is an increase of rpm on one of them then you need to do the carbs right away. I loved thes old 3 bangers, but that was their achilles heel. Better yet take it to an old OMC mechanic.

    Best regards,
  6. Brett

    Brett > PRO STAFF <


    Thanks Frank, now there's a trick I'd never heard before to diagnose a starved carb.
  7. Un-shore

    Un-shore Well-Known Member

    X2, That is freakin' awesome!
  8. rstevens

    rstevens I Love microskiff.com!

    Thanks for the tip on the carbs. But I just rebuilt all 3 and there are in good shape. She is running smooth on the horse and stays cool but, I don’t see any water coming out of the top end? Is this normal?
  9. Brett

    Brett > PRO STAFF <

    No whizzer tube indicated in the parts diagram, only a back pressure relief hole.
    Exhaust gases and cooling water exit down the exhaust housing.
    Only time I remember seeing water coming out the relief hole
    was spray when the outboard was running on the water.


    These are the only two spots, other than the prop exhaust, that show any water.
  10. rstevens

    rstevens I Love microskiff.com!

    Awesome thanks for the help!!!!!!!!  [smiley=1-beer-german.gif]

    not a lot of water on the exhaust side no.
  11. Brett

    Brett > PRO STAFF <

    On the older motors, an engine temperature gauge was considered a necessity.
    Most came with the sending unit already installed on the block.
    And if you don't know when the impeller was changed last, then it's time to do so.