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  1. #1

    Default 1980 70hp Evinrude

    Bought a boat last fall with a 1980 3 cyl. 70hp Evinrude motor, 13.25x17 prop. The boat is a 14 foot fiberglass tri hull. Here's the problem. After the boat has been idling for a while, (like waiting for a skier to get ready), when you hit the throttle the engine just chuggs and dies. It does work pretty good if not towing a skier, but does also do it sometimes. Carbs have been cleaned, timing adjusted, and new plugs put in. Was wondering if this is a common problem, and how do we fix it. And could we have the wrong size prop on this boat. Can't test that as we do not have a tach on the boat either. Please help!

  2. #2
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    13,816

    Default Re: 1980 70hp Evinrude

    On a 35 year old motor you need to do a compression test.---Post the results.

  3. #3

    Default Re: 1980 70hp Evinrude

    Thanks will give it a try and post.

  4. #4

    Default Re: 1980 70hp Evinrude

    If I do a compression test on my motor, do I need to put the muffs on it, or can I just bump the starter?

  5. #5
    Join Date
    Aug 2007
    Location
    crossett, Arkansas, Ashley
    Posts
    8

    Default Re: 1980 70hp Evinrude

    Quote Originally Posted by VickyW View Post
    If I do a compression test on my motor, do I need to put the muffs on it, or can I just bump the starter?
    To do a comp test correctly pull the kill switch. Hookup the comp gauge. Open throttle all the way. Spin motor till the gauge reads its highest. Usually will be about 5 or6 complete revolutions. Move to the next cylinder. Oh yeah have all the spark plugs pulled

  6. #6

    Default Re: 1980 70hp Evinrude

    Did the compression test, top cylinder was 125, 2 and 3 were both at 130. Now where do I go from here. Thanks for you help so far!

  7. #7

    Default Re: 1980 70hp Evinrude

    Took the boat out again today, same thing, if it idles for a while it bogs down when you hit the throttle. I am at whits end trying to figure this out!

  8. #8

    Default Re: 1980 70hp Evinrude

    Sounds like the carburetors could be loading up, have you done anything to the carbs?

  9. #9

    Default Re: 1980 70hp Evinrude

    Quote Originally Posted by VickyW View Post
    Bought a boat last fall with a 1980 3 cyl. 70hp Evinrude motor, 13.25x17 prop. The boat is a 14 foot fiberglass tri hull. Here's the problem. After the boat has been idling for a while, (like waiting for a skier to get ready), when you hit the throttle the engine just chuggs and dies. It does work pretty good if not towing a skier, but does also do it sometimes. Carbs have been cleaned, timing adjusted, and new plugs put in. Was wondering if this is a common problem, and how do we fix it. And could we have the wrong size prop on this boat. Can't test that as we do not have a tach on the boat either. Please help!
    . What is the situation with your water pump impeller and thermostat I'm wondering if your engine is overheating does it diesel?

  10. #10
    Join Date
    May 2011
    Location
    slough ,berkshire uk
    Posts
    161

    Default Re: 1980 70hp Evinrude

    a 13.5x15 pitch will fly out the hole, a 17 is not a ski prop unless you vent it.
    the bogging down is bad idle circuit in he carbs or timing not correct. hope your running champion plugs and not ngk!!!


    here is 13ft tri hull holshot with a 60hp evinrude tripe running 13.5x15 to show what it should be like.

    go to you tube and type in
    phill nutter prop.

    I cant post link here for some reason ?

  11. #11

    Default Re: 1980 70hp Evinrude

    delete to old

  12. #12
    Join Date
    May 2011
    Location
    slough ,berkshire uk
    Posts
    161

    Default Re: 1980 70hp Evinrude

    carbs need a good clean, then re sync.
    also check jets for your elevation !!!


    dont know why someone put too old delet
    e, the post is not too old.

  13. #13

    Default Re: 1980 70hp Evinrude

    Quote Originally Posted by phillnjack View Post
    carbs need a good clean, then re sync.
    also check jets for your elevation !!!


    dont know why someone put too old delet
    e, the post is not too old.
    Check the date it's 7 months old OP last responded in 08/2015 I deleted my comment because the post is to old and they are gone. More than happy to teach you something again.

  14. #14
    Join Date
    May 2011
    Location
    slough ,berkshire uk
    Posts
    161

    Default Re: 1980 70hp Evinrude

    7 months old too old, are you nuts. 7 months is not too old.
    3 years maybe, but 7 months you leave it on.
    many people around also look for advice on this very subject, so it should be answered . and answered correctly.

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