Prop Nut

[DTro]

My late 80’s Merc 25 has a nylon prop nut, not just an insert, the whole nut is nylon. There is no cotter pin or anything either.

I haven’t had an issue with it ever, but the other day I put a rebuilt prop on and tightened the nut. I guess I must have ate my spinach that day because I went too far.

It is on there pretty snug right now, but with enough torque I can still turn the nut. I’m not really comfortable leaving it that way, but maybe it’s ok?

With all the debris I hit during the year, a cotter pin would put me at ease.

Any thoughts on this design. Is there supposed to be a cotter pin? I don’t see a hole, and the nut isn’t a castle type.

[BoxMN]

I do know that you want to use a new nut if you have removed and put it back on a few times at most, at least with the regular nuts. Maybe just go get a new one. It can't cost much.

[Eric Wettschreck]

Darren, sounds like a Nylock style nut. They do a good job of holding things in place, but once overtightened they have a tendency to strip or elongate the threads, thus reducing their locking capability.

If it were me (It's not, but if it were) I wouldn't go drilling holes in my prop shaft for a cotter pin, I'd just get another nut. They are fairly inexpensive.

[marine_man]

That's the way they are... plastic. I'd pick up another one and wait until your shirt fits again before tightening it

marine_man

[Black_Bay]

Darren, sounds like a Nylock style nut. They do a good job of holding things in place, but once overtightened they have a tendency to strip or elongate the threads, thus reducing their locking capability.

Actually they are entirely made of nylon/plastic. In fact I'm looking at one right now. They are very easy to strip if you're not careful. I'd just get a new one and use a torque wrench to tighten it to specs.

[DTro]

Cool thanks guys!

Does it have to be a special prop nut? I guess I can just pick one up at a marine place huh? I should pick up a prop wrench to have in the boat anyways.

[marine_man]

I'm pretty certain it is a special nut...

marine_man

[Eric Wettschreck]

My guess is that it's not a standard thread. A marine place would be the place to go.......I'm guessing.

[mn_bowhunter]

They are cheap. I put a new prop on an 88 20 horse merc last summer and the nut was like $2-3. I didn't torque it, just snug as per dealer recommendation. He said to replace it whenever you take the old one off because they will get to weak to be reinstalled as they age. The original made it 20 years so I guess they work well enough