Merc outboard, 7.5, Help w/ stripped lower unit upper oil vent screw!!!

[abk]

Just got back on the hard from 2 weeks of Blue water Sailing off the coast of N.J. Milky oil (small amount) Leaked from the prop when out of the water.

Removed the Vent Screw and lower plug and water and black oil residue came out.

The vent screw was a small machine head screw with no washer, paper, nylon or composite washer. The p/o must have replaced it and I do not know what should go in there.

Also, when I went to put it back in, I couldn't get the screw to bite and tighten. After trying numerous times to work it in tight (never was able to) I THEN DROPPED AND LOST THE SCREW!!! (did I say my last name was "screwup"?)

I then bought a replacement screw ( longer that the original) and it wouldn't bite either...

So, I assume I need to tap the hole and replace it with a larger screw... Before I do that, it goes in on an angle and a larger screw head may not fit in the space on the lower end of the motor... Perhaps I can grind the head to fit...

Looking for opinions, advice and any ideas on the fix...

Like,

Epoxy it shut permanately?
Epoxy, Liquid metal it and then tap it?
Just tap it?
What type of sealing washer could be used?
Can I duct tape it?

I hate to think that a little screw beat me up for hours and it finally won...Thanks in advance for any help...

 

[Don12364]

If the casing is thick enough, i.e. about 3 threads, you could use a helicoil. They are normally stainless.
I would imagine it is a metric size unless the engine was made in USA.
You will need to open the gearbox to remove any drillings and the small end of the spring.

http://www.helicoil.com.sg/HeliCoil-Installation-Instructions.htm

 

[kloudie1]

Donalex is right, A Helicoil would be a great solution .. Ya probably want to take the engine to a qualified outboard mechanic since the gearbox disassembly/assembly is critical.. and that is the only way to be sure that the chips are all out. While there, have the water pump impeller changed and the prop shaft seal and the driveshaft seal as well. Good luck with it.

 

[Stu Jackson]

Bruce, same thing happened to me on the same engine years ago. Helicoil worked just great for many years. That's the solution.

 

[jimmyb]

Bruce,
When you say it wont "bite", do you mean it will not start in the threads or it will not tighten due to being stripped. If the latter you can helicoil as has been said. If it isnt stripped just take the appropriate tap and grease the threads, pass it through the hole and back to clean the burr and the grease will grab most of what is fouling your threads. Of course if you helicoil, the grease trick is not going to be sufficient to catch all the drill and fresh tap chips. I would tear it down for that as well.

jimmyb

 

[Douglast]

the screw would probably stay in and seal ok if you wrapped it well with teflon tape till you had other work to do..or twist an ear plug into it..lol..

 

[RAD]

Try getting the original screw from a dealer and see if that fits better

 

[wonkodsane]

Teflon tape is pretty magical stuff, very resistant to oil.

Silly though it sounds, you can also take Nitrile disposable/sterile surgical gloves and cut out some of the material to use as gasketing in situations where the gasket may encounter warm or hot oil. Make sure it is Nitrile as latex, vinyl, and polyurethane will not survive those encounters for long enough to be safe.