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Stripped threads on lower unit

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Al Lang

New member
I have an older 35HP Johnson Seahorse..In changing the oil, I stripped the inside threads out on the top vent hole. I found a 3/8"-16 ID self-tapping insert that I am going to drill out a 33/64" hole and screw it in. When I drill out the hole, how deep can I go in with the bit without hurting anything on the inside of the lower unit housing? I thought I show a little piece of aluminum or a stopper on the inside back of the hole. Should I use a permitex or a loctite to better seal the new threads? Are the aluminum shaving anything to be overly concerned about? Thanks:confused:
 
Al Lang said:
I have an older 35HP Johnson Seahorse..In changing the oil, I stripped the inside threads out on the top vent hole. I found a 3/8"-16 ID self-tapping insert that I am going to drill out a 33/64" hole and screw it in. When I drill out the hole, how deep can I go in with the bit without hurting anything on the inside of the lower unit housing? I thought I show a little piece of aluminum or a stopper on the inside back of the hole. Should I use a permitex or a loctite to better seal the new threads? Are the aluminum shaving anything to be overly concerned about? Thanks:confused:
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I would get the diagram for the Gearcase and look at where your drilling.
 
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Yes the shavings would be a problem as they will wind up in your lower unit oil maybe taking out the bearings or bearing surfaces. You might try finding a replacement leg. You wouldn't need the gears or the skeg. What model do you have? Lots of years will interchange.
 
It would be worth the effort to disasemble the gear case and drill out for the next size screw, but here's the catch, the shoulders on those screws will be too big for the counterbore. You would have to determine if there's enough material to either make a bigger counterbore or leave the head of the screw hang out, or grind the screw head down to fit the original counterbore. Tricky situation at best, those castings are made to conserve as much weight as possible, so the metal is thin. A plastic washer for a gasket should do the job to seal it. But yeah, no metal shavings in the gear case at all cost.
 
It would be worth the effort to disasemble the gear case and drill out for the next size screw, but here's the catch, the shoulders on those screws will be too big for the counterbore. You would have to determine if there's enough material to either make a bigger counterbore or leave the head of the screw hang out, or grind the screw head down to fit the original counterbore. Tricky situation at best, those castings are made to conserve as much weight as possible, so the metal is thin. A plastic washer for a gasket should do the job to seal it. But yeah, no metal shavings in the gear case at all cost.
 
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