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  1. #1

    Default Advice on 15hp block damage

    Have a 1978 15hp that had a corroded water cover plate at the bottom in front of the thermostat and also noticed a smaller leak on the top of the head, so decided to replace head gasket together with the water cover and it's gasket.
    When I took the head gasket off did not expect to see this at the top of the block.
    What's best to do here guys?
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  2. #2
    Join Date
    Sep 2010
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    Default Re: Advice on 15hp block damage

    Water pressure is not that high.----Simple repair with any of those popular aluminum / epoxy putty materials.

  3. #3

    Default Re: Advice on 15hp block damage

    Many thanks Racerone. Thought to use JB Weld but will it grab well in those very small nicks?

  4. #4
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    Sep 2010
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    Default Re: Advice on 15hp block damage

    Actually ---Myself I would use a product called ---Lumiweld-----But I do not know your skill set.----I assume most folks learned to make mud pies used playdough in younger years.----Sorry, I could not resist a bit of humor.

  5. #5

    Default Re: Advice on 15hp block damage

    Good one! Will look into Lumiweld...new to me.

  6. #6
    Join Date
    Nov 2011
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    Default Re: Advice on 15hp block damage

    Quote Originally Posted by Snapper Fisho View Post
    Many thanks Racerone. Thought to use JB Weld but will it grab well in those very small nicks?
    It'll work as well as any.

  7. #7

    Default Re: Advice on 15hp block damage

    Appreciate the support from you guys who are a lot more experienced at all this. Cheers

  8. #8
    Join Date
    Jun 2013
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    Duluth Mn
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    Default Re: Advice on 15hp block damage

    Ha! Make sure clean and roughen a bit before application of chosen epoxy. Flatten when time is right. This will be a fine repair. For me, if I had the block completely dismantled, I would mig with 4043 filling alloy using a rich supply of pure argon. Don't forget to surface the head before installing. You must know how to properly do that, eh?

  9. #9

    Default Re: Advice on 15hp block damage

    Quote Originally Posted by timguy View Post
    Ha! Make sure clean and roughen a bit before application of chosen epoxy. Flatten when time is right. This will be a fine repair. For me, if I had the block completely dismantled, I would mig with 4043 filling alloy using a rich supply of pure argon. Don't forget to surface the head before installing. You must know how to properly do that, eh?
    Thanks timguy. You guys have really reassured me. Will do that and I know how to surface head as did it on my 4hp lightwin. Used 120 grit and then 240 grit on a glass panel working in figure 8 motion. Came up a treat.
    I don't know how to mig but wish I knew.

  10. #10

    Default Re: Advice on 15hp block damage

    Had another look at it during the day and the top of the block is actually a little depressed in the middle region, not perfectly horizontal. Haven't seen that before but I gather that shouldn't be a problem either.

  11. #11
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    Default Re: Advice on 15hp block damage

    No problem, those cast aluminum parts are sometimes kinda crappy looking. Love mig working, I've wanted to weld aluminum since I was a young kid....back then you really had no way to do it. Mig was still in development. I think Ford started using mig steel welding in the early 6O's

  12. #12

    Default Re: Advice on 15hp block damage

    It's so satisfying to realize your dream timguy and become good at it. Well done and it shows from your posts.
    I started with an early 80's OMC V4 motor and have grown to love the Johnson/Evinrude era. Such brilliant quality and my 115hp is still going well and as strong as ever.
    I now have started a collection of vintage motors from the 60's and have learnt so much since my first water pump overhaul years ago, changing water deflectors and a head gasket, learning both cdi and magneto ignition and more recently realizing how important synchronizing dual carburetors precisely is after a carby overhaul.
    I enjoy quite a bit tinkering with OMC two stroke outboards from those golden years!

  13. #13
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    Default Re: Advice on 15hp block damage

    Amen, brother. This modern engineering just lures folks in, once you get comfortable with it, then it turns on ya! You say....WTF is wrong now....? Might take 10 years or so, but I assure you it's gonna happen. Early engineering is far from flawless, may not be the most efficient, and certainly not as complicated, allowing idiots like me to hang on to what I know and trust. I rely on that engineering every time I take family or friends back in the wilderness.

  14. #14

    Default Re: Advice on 15hp block damage

    Well I totally agree and it's won me over too.
    Now, I have a question as I think I stupidly stuffed up with this 1979 15hp by connecting my garden hose with an attachment to the copper tube after putting the head and water cover back on with new gasket. I've done this before on other motors but my water pressure is higher now than in past and for some reason water entered both cylinders! It was expelling fine from the exhaust and tell tale as I cleaned all passages out I could get to but never has this happened to me before, so is it possible that with my water mains being stronger in our home now, that I foolishly did not take this into account and it force water between the head gasket sealing metal around the cylinders? I'm disappointed with myself if I forced too much water pressure through the copper pipe by doing that.

  15. #15
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    Default Re: Advice on 15hp block damage

    If water got INSIDE the engine then you have to get it out ASAP .----Yes ASAP.----But I doubt water pressure was high enough to get by the gasket. !

  16. #16

    Default Re: Advice on 15hp block damage

    Thanks Racerone for your quick response. I am doing that now and I am at a loss why. The water pressure I have now is high and can't think of any other reason atm. I was careful with the cylinder head, head gasket and block surface as in the past. When I got this motor, it had a seized powerhead but I put ATF in both cylinders and left overnight then with wrench and correct socket I put gently pressure back and forth on flywheel and it came good and moved freely. Cylinders had no rust other than a mild line in top one partly following the circumference of I assume one of the rings.
    I just am at a loss right now. This motor came stock with the Champion Surface gap plugs L78V. First one I have like this.

  17. #17
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    Default Re: Advice on 15hp block damage

    Part # of the new head gasket you used ?

  18. #18

    Default Re: Advice on 15hp block damage

    Quote Originally Posted by racerone View Post
    Part # of the new head gasket you used ?
    Sierra 18-2963 (330818)

    Looked exactly same as original racerone

  19. #19

    Default Re: Advice on 15hp block damage

    Been pouring two stroke oil down the cylinders and rotating flywheel. Looking at the block there is one water inlet on bottom of cylinder 2. The head gaskets only have one cut out on the top of cylinder 1 where the water would enter from the bottom inlet on the block with a single outlet circle the size of head bolt hole diameter on the bottom left side of the head between the head bolt and thermostat. This also has an opening into the water cover. That would have created a lot of added water pressure to escape particularly as the thermostat would be closed with me only feeding water to the copper tube? I just feel pretty annoyed at myself at the moment.
    Last edited by Snapper Fisho; 01-15-2022 at 11:30 PM.

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