What causes the Prop nut to get loose

[BoatGoFaster]

I tighten it with a breaker bar, very tight. I use the tab washer to lock the nut. So how do these things loosen up??

thanks

[DaveR]

Are you using the correct thrust washer? It could feel like the nut loosed up if the taper is wrong or shot.

[us1]

Usually its ware on the thrust washer.

[BoatGoFaster]

How does the thrust washer wear? dont the washer, prop spin as one thing, held tight together by the prop nut?, which can not move, because of the tab washer?

thanks

[us1]

Yes that is true, but the prop is under extreme forces causing it to move around on the thrust washer and prop shaft.

[BoatGoFaster]

So is the solution, just to retighten the nut periodically?

[H2Onut]

read an article from a URL someone posted, It claims nuts back off from vibration, not stress, might want to see if changing props makes a difference. Maybe it is out of balance and causing excessive vibration and thus causing the nut to loosen.

[us1]

Yes the solution is to check and retorque periodically, all mine do it, you will see the ware if you look at the thrust washer closely.

H2Onut if the is torqued right and the locking tabs are bent down properly the nut can not back off. An out of balance prop can however ware the thrust washer pretty fast.

[Jay Smith]

And always remember that a prop trys to walk backward (off ) only in reverse. In forward the prop is trying to move forward on the prop shaft. On all righty and I guess it's the oppisit on leftys , huh John ?

Jay @ JSRE

[us1]

I don’t have the luxury of reverse on my lefties, well the Silverwing does.:cool:

[Promax300]

they make 2 different thrust washers one is very soft , try to find a hi perf one .

[BoatGoFaster]

I think part of the problem is when you keep your boats on a lift it is not as easy to do things, such as tighten the prop. For next year I am going to set up some sort of floating platform/ work boat so that I can get to the motor without putting the boat on a trailer.

[DaveR]

Hey Boatgofaster -

Do what I do - Jump in!!! In the spring it's a real thrill!

[BoatGoFaster]

Those things got Theeth!!!

[AnthonySS]

If the taper on the inner Thrust washer is good and the prop is good, I also recommmend 2 fresh prop nuts per season. Especially for those of use that "on-off" props a lot as the Elastick (nylock) wears after time too.

Fresh "Nuts" (Prop) always cure my backing off problems and they are cheap insurance. On mercs at least one bent tab should also ensure tightness.

[DaveR]

Hummmm. Now that's a problem we don't have in Michigan. How about chuming the other side of the dock?:D

[Flat Out]

On my OMC the nut will back off over time. Everthing is good. In the sping I put on my prop tighten everthing, install the cotter pin. The pin will rattle around. Over time the pin is tight, meaning the nut has backed off. The best insurance is to check the nut torque periodically. Like Anthony said with the Mercs use a fresh nut. With the OMCs make sure you use the right size STAINLESS STEEL cotter pin. Always a good idea to keep a few spare parts in your toolbox.

[H2Onut]

Here is a link to an interesting article on bolt loosening problems.

Enjoy, Mike


www.boltscience.com/pages/vibloose.htm

[pyro]

Mine never loosens up! Thrust washer fits good. The nut isn't even nylock. It's the nut from a prop-lock, but the lock was lost. It's just a plain, brass nut. I use a lockwasher with it, but the washer's teeth are always lying against the "tight" side of the teeth on the aft nut.

[BK]

When we were racing Mod-C 30hp Yamaha's, a buddy of mine with the same motor, was a Mercedes mechanic. One day he tried a Mercedes wheel locking lug nut on his prop shaft.... Perfect fit! He brought these 'trick' prop nuts to the next race and handed them out to us as gifts. They worked super!

But we *always* removed them after each race, so there's no telling how they'd endure over an extended amount of time. :)

[Firestarter]

It is the thrust washer that is causing what appears to be a nut backing off.
With a surfacing prop their is a natural tendancy fro the prop to work back and forth (top in bottom out) all the way around. To look at it another way, their is the full force of the thrust from the propeller pushing on you thrust ring, but if you are surfacing only the bottom half of the prop is pushing, and hence uneven pressure on the ring. This wears it out.
I replace thrust rings all the time ( I keep a consideracble inventory of them ) and each prop has it's own thrist ring. The prop nut CANNOT losen or come off with mercs locking tab system.
I have used prop nuts that you can turn on by hand (OMC is like that)and as long as you lock the tab down you are good to go.

RT

[us1]

True Firewalker, I have some thrust washers that are worn down to a nub.