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Thread: Johnson thermostat issue

  1. #1

    Johnson thermostat issue

    We have a 1984 Johnson V4 115 HP. We are trying to check the thermostats and have the middle bolt removed. The two side bolts are stuck fast. Repeated attempts to move the bolts with a ring spanner have resulted in the hexagon heads becoming rounded. It is no longer possible to get a grip on the bolts. Is it safe to weld something onto the heads using an arc welder? We are worried the thermostat cover may melt or that the electric current might burn out the alternator.


    Would it be better to apply heat to the bolts using an LPG flame?

  2. #2
    Ausfish Platinum Member
    Join Date
    Mar 2015
    Location
    Kalbarri, WA

    Re: Johnson thermostat issue

    I would carefully apply heat to the bolt head. If you can get at it from the side, and there is nothing behind it in the line of fire of the flame tip,, sort of have just the edge of the flame on the head to keep it away from the casting. The paint is pretty tough. I have just had to do this to remove two frozen bolts from the lower unit of a 9.9 mariner which hadn't seen a spanner in decades. Started with a socket, tried rings, open enders...even tried an impact driver, but the force applied to the uni joint I had to use destroyed it. So, as a last resort, I heated it as described with a Mapp gas burner, then grabbed it with a set of vicelocks with good sharp jaws, and they both came out. Paint is still intact.

  3. #3

    Re: Johnson thermostat issue

    When reassembling nothing like a dab of Nickel anti seize on the thread .

    DoNotFeedTheTrollsAandBelligerent

  4. #4

    Re: Johnson thermostat issue

    Dear all,

    Thank you to the Members who kindly responded to my last request. Unfortunately it has taken me some time to respond but we're now in a position to report on progress. My (well qualified) mate reports the following and, again, we're after advice please?

    We have checked the water pump and thermostats in accordance with your advice and they seem to be in order


    A compression test shows 121 and 122 psi on the RHS, 108 and 116 psi on the LHS. There was water in the lower RHS cylinder so we took the head off the RHS. The inside fo the head is shiny clean confirming the entry of water.


    The water passage around the cylinders was completely blocked at the restrictor between the cylinders so that water flow to the head would be available only through two small holes one at the top and one at the bottom of the gasket.


    This may have caused the head to warp ( .004" - .005" measured ).


    Would this be enough to allow combustion gases to escape into the water passages?

    Regards

    Richard Farrell

  5. #5

    Re: Johnson thermostat issue

    Yes thru your cylinder head, when it lets in water it lets out gases too did the shop machine your head and measure the surface of the block too?

    when u weld on outboard blocks that's are assembled u need to remove the electronics otherwise it'll fry them because it's all earthed to the block disconnect your batteries also

    i find my self in your situation very often i don't mess about with broken bolts, 2 ways of getting them out 1 is a welder the other is replacing small parts like your thermostat cover i possibly would have ground the bolt head off than removed the thermostat cover its likely it would be ruined than take a grinder and slowly grind down on what bolt is left sticking above the block the heat from the grinder will break the salt and calcium deposits around the bolts thread make sure u leave a little bit of bolt sticking out to grab with snap lock pliers than wiggle it back and forth ever so gently untill it free's up

    welder is the go for those really seized bolts tho i use mig welder to weld the nut on than i use the tig to heat the nut 4 times allowing 15 mins cooling they undo easily

    shops charge $110 per each seized bolt to be removed

    these two bolts on a Johno 225hp were probably the worse i have ever seen, 1 hour of work they both came undone


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