Johnson Md-39 Cooling System

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  • The Boat House


    Replies: 4549
    Topics: 111
    #20720

    Plugged fuel line is something worth checking for also.
    Squirt some carb cleaner on a pipe cleaner and stick
    it in there and see what you get.


    willyboy


    Replies: 106
    Topics: 21
    #20722

    Thanks Tubs,i’ll give that a try while everything is apart.


    marvk


    Replies: 56
    Topics: 12
    #20765

    Glad to hear you got it running and the cooling is working for you. Mine still has an overheat condition. I’m guessing the watertube, or one of the passageways in the head has crud in it somewhere. It seems to run well until it starts to overheat and then I can hear the sizzling of the water, or worse, the fuel mixture, around and near the carb. 😯


    willyboy


    Replies: 106
    Topics: 21
    #20771

    MarvK I pulled my carb off for a cleaning and the water jacket is right behind the choke side of the carb. They used some type of thick brown paint to coat the inside of the water jacket surrounding the cylinder.On a good note I happened to be in advance auto parts last nite and found a roll of felpro #3157 rubber-fiber sheet 1/32" that matched pretty close to the type of gasket behind the carb covering the water passages. When I had the lower end apart I took the entire piston pump apart and degreased and cleaned each piece and then put back together with some lubriplate 105. When I shook the assembly before I put it together I could hear both brass check balls rattling-one was stuck in the cup before I cleaned it and I had to knock it loose and then polished it with some #0000 steel wool. I also ran a piece of 1/16" tig wire up the water tube to see if anything was clogged.Also something I noticed was the faceplate on the end of the copper ram that rides on the lobe of the propshaft had a wear groove in it from use,i changed it out for the one Doug sent me along with the rest of the parts-it had a much better surface to contact the propshaft lobe.


    Mumbles


    Replies: 5764
    Topics: 298
    #20775

    If the lobe is all gnarly and wearing out the end of the pump plunger, it can be resurfaced in a lathe using a four jaw chuck.


    willyboy


    Replies: 106
    Topics: 21
    #20777

    Nice work Mumbles,makes me miss my machine shop days where I had access to all those goodies to do that kind of work. I can see this hobby could get more expensive then it already is if I start shopping for "those" kind of tools but then again I been eyeing one of the portable mill/lathe combos for a while now….

Viewing 6 posts - 11 through 16 (of 16 total)
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