Overhaul your own outboard motor

Discussion in 'Boating' started by crackers, Oct 19, 2006.

  1. crackers

    crackers New Member

    Messages:
    296
    State:
    Arkansas
    Has any one overhauled your own out board motor like replace a piston or reboured the cyls or what and if you did would you do it again and what kind of problems did you have. The reason im asking iv can pick up an 80 hp Murk
    86 yr that might need a piston.or no compression any ways and was wondering if it might DIY repairable might just be a stuck open valve dont know havent picked it up yet... Thanks great site
     
  2. Mr.T

    Mr.T Active Member

    Messages:
    2,554
    State:
    MO
    Bored and replaced some burned pistons in a 77 Johnson 35hp - no big deal really, you need to be mechanically inclined and have a proper service manual.

    The parts are more expensive than you think and the work will take longer than you expect.
     

  3. crackers

    crackers New Member

    Messages:
    296
    State:
    Arkansas
    I was wondering about the parts i suppose they are pretty expenceive but i think if i take my time and keep it really clean and tighten the nuts and bolts to spec. I should not have a problem. I can check the service manual out at the public library. I think i just might give it a whirrl. thanks
     
  4. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    You can forget the stuck open valve. There aren't any in that engine. I have over hauled several different outboards and on each one you will find different problems but each can be delt with. as was posted a manuel is a must.
    You have the right ideal with keeping every thing clean and tighten to spec.
     
  5. my4x4awd

    my4x4awd New Member

    Messages:
    105
    State:
    TN
    I just completed a complete rebuild 1986 Evinrude 70 HP. I have overhauled auto and other small engines. I got some great advice from BP and BC here on the board. Now I have a engine that should last me another 20 good years. What they are saying is correct. Read, read, ask and get a manual. Good luck Craig

    PS Bubba/Bob ran great on the maiden voyage last Saturday!!!!!!!!!
     
  6. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Did you use a 25:1 break in mix for your gas. It's a must for the first 10 hrs.
     
  7. crackers

    crackers New Member

    Messages:
    296
    State:
    Arkansas
    I havent got this engine yet but the owner told me that it did not have any compression on one cyl. So my first thought was it could be a hole in that cyl. or the piston may have broken off at the crank but without tearing it down I dont know. Picking it up Sunday and will know more about it. I have never overhaled an outboard but,I think with all your kind folks that are helpful and a good service manual.I should not go wrong... thanks
     
  8. Rookie12

    Rookie12 New Member

    Messages:
    1,324
    State:
    Kannapolis, NC
    If you know your way around an engine, then you should be able to build it. From what I hear, it's usually stuck or broken rings or scored cyliner walls. I talked to my uncle the other day and he was telling me that when he was a kid he had a friend that had an old 50 hp Merc that had burned a hole in a piston. It had a small pinhole in the intake where water got in and took out the piston. The hole was a casting imperfection the just let loose. Anyway, he said they pulled the head off and epoxyed over the hole in the intake where the water had got in and they cleaned up the hole in the piston and actually tig welded the hole shut, ground it down, smoothed it out and he ran that engine for 4 more years before selling it. Talk about making do with what you got!!! Bubbakat, Bobpaul, ya'll ever do anything like that?! I gues you make do with what you got!! just thought that was interesting.
     
  9. crackers

    crackers New Member

    Messages:
    296
    State:
    Arkansas
    If this motor has a hole in the piston, I just might try that I think there are some very good welders around that should be able to weld that up for me ( if that is the problem) should be a lot cheaper than a new piston if a guy pulls out both pistons and pulls the wrist pins out and grinds the piston back to the right height, then grind the bottom of the skirt on each piston till they weight the same that would work, thank you very much for that info will look into that.. cheers
     
  10. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    I have an '80 Evinrude 75 and got the factory shop manual on Ebay for about 20 bucks, shipping and all. The Seloc manuals are good, but for the same money or less you can probably find the actual shop manual on Ebay and it will save you the time of thumbing through 20 different models and years in the Seloc and Clymer manuals. The boat I bought this summer came with a blown 70 Johnson, so that's my winter project. Not a spokesman for Ebay, but you can probably find a rod and piston set for less than the machine shop will charge to fix a bad piston (if that's what it turns out to be) BobPaul would know if that's a viable alternative or not. Good luck with it!

    Branden
     
  11. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Welding a piston or epoxy on a cyl wal is a one in a million shot.

    Just pull the head over the cylinder with no compression and you'll see the whole story.

    Go over the wiring real good and look at the condition of the insulation, corrosion, or any other problems with it.

    Be ready to rebuild the carbs.

    Don't trust the lower unit either.

    Try to check for spark on all cyl's. It's already broke, cranking it can't hurt too much more.
     
  12. 710split

    710split New Member

    Messages:
    31
    State:
    iowa
    by putting something here, I'll get an Email so I don't miss anything.
     
  13. crackers

    crackers New Member

    Messages:
    296
    State:
    Arkansas
    Picked Up the engine yesterday and will start looking into it in the very near future. It is an 85hp model 850 merc 3 cyl will check the compression to see which cyl that has no compression. then will pull the head and go from there.

    I will get a service manual for it before i even tear into it and keep it clean.
    Pistons on line are about 100.00 each and are at .010 to .040 over will check and see if head needs a rebore which im sure it will. but i think im going for it . Wish me luck as slow as i am it might take me all winter long tho. cheers
     
  14. crackers

    crackers New Member

    Messages:
    296
    State:
    Arkansas
    Got the motor unloaded from the back of the truck,setup a treated 2x8 between two trees, put that on after i unloaded the motor (boy was that one heavy hog to unload almost too much for me and my wife and my granddaughter but with a little fanagling we got it up,and standing,checked it for stability. low and behold it has 4 count them 4 cyl insted of three all seem to go up and down. now going to take compression test of all cyl and see what each one is. going to do this one small step at a time .
     
  15. zappaf19

    zappaf19 New Member

    Messages:
    1,574
    State:
    Monticello,IN
    Take your time and take pictures. You should be fine.
    Bill
     
  16. Mickey

    Mickey New Member Supporting Member

    Messages:
    14,592
    State:
    Illinois
    Jerry: I wish you success on your winter overhaul project. We all need projects to take care of cabin fever and you have a big one. Keep us posted,