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hovermn

Stripped lower unit oil screw

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I have a '90 30 hp Johnson, and today I managed to cross thread one of the lower unit oil fill screws, and stripped the other. The weird thing is, it was easy going while cross threading the one, and the other never hit that just right mark while tightening.

So what's the damage? Is there a way of repairing this without replacing the lower unit housing? Besides maybe silicone or JB weld (can't stand that stuff) is there a proper way of repairing this?

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re-tap the holes a bit bigger and get bigger screws to fit?

Never done it but I don't see why it wouldn't work. Had to do it on my car after the good folks at wally world cross threaded the plug during an oil change

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I would go with a Heli-coil repair kit, very simple proceedure. I think you can find them at northern tool, just bring your plugs in so you can match up the threads.

Tom

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This is good reason to always thread a screw in by hand for atleast a couple turns. Its hard to crossthread with no tools.

Heli-Coil is the proper fix only if you still have enough sealing surface for the gasket to seat against after the hole has been drilled and re-tapped. If it is only the heli-coil the gasket will be setting against then it won't hold a seal no matter what you do. Depending on the thread size it may or may not be possible, and if I remember correctly those are pretty coarse threads, which makes the heli-coil thicker, making the drill and tap size that much thicker. Figuring out a way to drill and tap it bigger without getting metal shavings inside the housing is also going to be tricky.

It may be best to look on [email protected] or the used outboard stores and find a housing for cheap and swap out the internals.

Good Luck!

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If you get to the point of pulling the internals out of the gearcase, why not have a look at a competent welding/machine shop weld up the stripped holes, then re-cut the threads and sealing surface. Not cheap but it has to be less than buying a new gearcase housing.

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jb would work.. but you would not be able to change the oil easily.. what you could do is pull it apart drill it out tap it and get a new flat headed bolt.. clean out the shavings and be more carefull next time (:

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if they are actual drain plugs they may have a tapper to them, you might be able to go to an auto parts store and see if they can size a self tapper plug to match the ones you have. they maybe metric but unless they are actual mounting bolts i dont think they will be a regular thread bolt.

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Thanks guys. There's a lot of good advice here. I need to take a closer look at it again to see what I'm up against. It was raining when I did it, so when they stripped, I was done. There is some material left, and a friend suggested in the short run to wrap each plug with teflon tape good and thick, see if that holds until I can find a proper fix or a shell.

I'm also thinking about drilling and tapping larger holes and making my own plug. There should still be plenty of surface for the rubber o-ring to mate against. I learned a decent tip a little while ago about oiling the tap to catch most of the filings, cleaning and reoiling often.

Again, it's probably best I look at the situation first. I'm looking for a blow up picture to see what's behind those plugs now.

I also know an aluminum welder. The prop shaft seal is blown (darn fishing line) so I may as well pull everything and have it welded.

I'll update my progress as I go.

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I ended up taking the motor to a pro that's been working on OMC's for 30+ yrs. He used an order style plug that has a little more length. chased the treads a little deeper, and managed to solve the problem that way.

So if you have plugs with the gasket vs. the o-ring, tap her out deeper and use the older style plug. 3/8 - 16 thread.

Thanks again for the tips, guys!

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