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Broken Bolt/Cracked Thermostat Housing

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  • Broken Bolt/Cracked Thermostat Housing

    Well I screwed this one up pretty good. I should have been applying heat early on. This is the thermostat housing on a 87 40 ETLH. Sure looked like it had never been opened. Maybe if I apply heat now I can get the bolt to come on out? Then take it somewhere to get it welded & hope can salvage threads. I’m fairly sure it’s a stainless bolt in aluminum housing. How would you fix it!?


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  • #2
    if it was a housing you would buy a new one, but your pic shows it if the block itself
    pealing the broken part out ,cleaning it all up and welding, machining, drilling and tapping, is my only thought

    what did you do to crack that.
    I take it was not that way when you started
    Last edited by 99yam40; 1 week ago.


    • #3
      There was a small hairline crack there that I did notice which should have been indication for me to take it easy/try something else but I brute forced it-put too much pressure on the extractor bit, so I’m paying for it.


      • #4
        if it was already cracked then there is nothing you could have done.
        apparently corrosion had set up inside there and swelled it far enough to crack

        find a good aluminum welder and see if they will give it a shot.
        But you will need to remove the remains of the bolt and clean up all of the corrosion to weld it
        and then mill the surface flat and then find the right place to drill and tap.


        • #5
          New cly head or start with a good outboard in the first place. Yamaha's are very weak in the metal.


          • #6
            nope it is in the block not the head
            Yamaha Outboard Parts by Year 1987 OEM Parts Diagram for Crankcase - Cylinder |


            • #7
              99 yam you are correct.
              most therms are in the heads (top)


              • #8
                Local outboard shop says they have it fixed. I know they have a good aluminum welder that works with them, but will have to check out the work tonite. I know they drilled/tapped/inserted stud. We will see what it looks like. Now I just need to limit the boneheaded cromag attempts on my part…


                • #9
                  good to hear, what did they charge?
                  has to be better that a new block

                  Pic of the repair would be nice also


                  • #10
                    Well they charged 150.00. It looks like Cletus did the work. I'm not so upset about what they did drilling and tapping and their repair (no welding)-its that they threw metal filings everywhere without so much as putting down a dropcloth and then ran it! There is metal in the airbox, metal, metal everywhere. I wonder how bad the cylinders are scored. I guess I can't touch it without a complete teardown. I took a brief look at it before I Picked it up at closing time and didn't think things looked real good. Got it home and realized the extent. Not sure what to do, talk to an atty first thing in the morning or go have a chat with the mgr. and see what happens. This is why I haven't been to an auto repair shop in years. It looked like the shop had pretty good reviews online. I was really hoping they lied about it "passing the leak test" on the paperwork they gave me, it drained a little water out of the lower unit when I lowered the motor at home. Haven't taken the thermostat housing off to see if its wet in there. Maybe the water is from the rain we had today, but doubtful...I will probably head out there and take it off and report back....


                    • #11
                      they may not have actually ran the motor like that, maybe the pushed water thru it.
                      But I do not see how that would pressure up anything
                      all you can do is ask them about all the metal everywhere and if that ran it sucking metal into the carbs.
                      take lots pf pics of it to show them what you found or take it there befor cleaning

                      I do not understand how they could have fixed it without welding.

                      shop vac would be the best thing to suck up everything you can and then plug up everything you do not the shavings in and blow it all down with compressed air.
                      wear goggles to keep out of your eyes


                      • #12
                        Why o why are there SO many SHOPS/SLAKERS in this biz ??