Stripped or cross threaded lower unit drain plug

[pls418111]

I stripped or cross threaded my lower units drain plug on my 115 Yamaha, what's the easiest and cheapest solution? Thanks

[robert graham]

There are Heli-Coil products that can be installed...If it was me, I'd be willing to pay a marine mechanic to install it so it's done correctly...

[DennisG01]

I stripped or cross threaded my lower units drain plug on my 115 Yamaha, what's the easiest and cheapest solution? Thanks

Since you stripped the drain plug and not the casing, it's easy. If you can't easily clean up the threads, just buy a new one.

[robert graham]

I don't think he means the drain plug.....most likely he means the threaded hole that the plug screws into....

[DennisG01]

I don't think he means the drain plug.....most likely he means the threaded hole that the plug screws into....

Hmmm. You know, that would make more sense - given the SS vs Al thing. Good thinking.

Depending on how bad the threads are messed up, he might get away with running a tap in there? Lot's of grease on the tap to collect any shavings.

[DennisG01]

I don't think he means the drain plug.....most likely he means the threaded hole that the plug screws into....

Hmmm. You know, that would make more sense - given the SS vs Al thing. Good thinking.

Depending on how bad the threads are messed up, he might get away with running a tap in there? Lot's of grease on the tap to collect any shavings.

PLS, given that you're asking what to do, I'd assume you're not too familiar with either a tap or helicoil. I think Robert had the best advice of paying someone to do this. If you mess it up, you may end up having to buy a new lower unit.

[pls418111]

There are Heli-Coil products that can be installed...If it was me, I'd be willing to pay a marine mechanic to install it so it's done correctly...

Robert,
I was planning on taking it to a mechanic, there is just none available this time of year in my area. So I was exploring my options. I'm sure it's the casing that is cross threaded, I didn't want to pull the plug out until I knew my options. It's oozing a small amount of lower unit oil. Because the hole seems to be recessed in the unit and the hole is small to begin with I didn't know if heli-coil would be available or not. Are you sure for this particular motor that there is a heli-coil made?

[DennisG01]

PLS - are you saying this started oozing oil by itself, or do you think you caused this? Is the plug not in all the way? Is it loose - meaning, does it rock? If it's in all the way and doesn't rock, it might just need a new seal - I usually replace them every year, regardless of condition. $2 isn't worth chancing it.

[pls418111]

Dennis,
No I changed the oil, went to put the plug back in, the odd thing is it went in pretty easy but it seems to be slightly off to one side and it oozed about a spoonful in about a month. I think that the guy who changed the oil last year stripped it because I didn't turn the plug that hard. My concern is do they make a heli-coil small enough for that? I know what a heli-coil is but I'm not familiar with how to install them. Does anyone know if Yamaha makes a heli-coil for this? I can't be the only stupid guy out there that has done this, if it wasn't already damaged last year when somebody else changed the oil.

[DennisG01]

It's been years since I've done anything with a helicoil so I'll let others discuss that.

Is it possible that there was a piece of the old seal stuck to the casing? That might explain the situation better, since as you said, it went in easily. Well, hopefully it's something simple like that, anyways. They're course threads, so it's "usually" kinda hard to cross thread them.

[robert graham]

I believe there's another item similar to the Heli-Coil that is preferred by some marine mechanics but I can't recall right now the name of it....maybe research this a bit for the best product...

[ausnoelm]

OK, remove the plug and have a look at the threads, you might be able to restart it straight (with a new washer) failing that, a helicoil will fix it in a minute, easy job to do.

[rodbolt17]

you need to measure the thread size, out of memory, but DONT trust mine, its 8x1.25mm.
I can tell you the standard heli coil is to long and must be modified by clipping off about 4 threads.