Key Material for Bronze Prop

[SkiprJohn]

I'd like your opinion on installation of a bronze prop on a stainless prop shaft.

What is the proper/best material to use for the key? Is it stainless or bronze?

The key I removed was bronze but I could just as easily reinstall with stainless.

Should I use anti sieze on the shaft before installation of the prop?

Kind Regards,
JohnL

[never monday]

John,
The shafting I order always comes with a stainless key, no mater the prop.

[fstbttms]

Originally Posted by SkiprJohn

What is the proper/best material to use for the key? Is it stainless or bronze?
The key I removed was bronze but I could just as easily reinstall with stainless.

Prop manufacturers supply bronze keys with new props. I say go with bronze.

Originally Posted by SkiprJohn

Should I use anti sieze on the shaft before installation of the prop?

No. Lubricate the interior of the prop hub with a waterproof grease.

[Alan Wheeler]

SST key is the best. It will least likely corrode away. A Bronze key, although commonly used, is more prone to corrosion if you ever have an electrolysis problem or if the key material is slightly different to the Prop. STT is less prone. Bronze is used because it is a softer material and in some situations, it will shear before major damage to the shaft or prop has occured. But I suggest that situation is not going to be a common one and I would rather trust the robustness of the SST.
Use lanacote grease as an anti-sieze, it has no metalic compounds in it. Don't plaster it on too thick. You need to ensure the mating surfaces of the taper fit have made a good clean contact with one another.

[fstbttms]

I actually think either key material is fine. But in the thousands of boats I have serviced, I have yet to see a bronze key fail, for any reason.

[Alan Wheeler]

That's good to know. Maybe I am over playing the possible problem then. I had one just a few weeks back that had all but eatin away. How the guy actually got the boat onto the cradle for haul out beats me. It could have failed compleatly at any point on his travel from marina to cradle. I reckon it would have only taken a gnat to sit on one blade and it would have failed.:-)

[fstbttms]

In an extreme corrosion situation, I suppose anything's possible. But failed keys are very rare, IMHO.

[delmarrey]

Don't use any grease!!!! Use WD-40 if anything. Don't ask me how I know

Grease actually creates a thickness like a shim between the shaft and the hub and they may eventually work loose. That metal to metal fit should keep out water. Besides I have yet to see a prop attached so hard that a little heat and a puller combined couldn't pop it loose..........................._/)

[Alan Wheeler]

Yes you are probably more correct by using the WD40 than a grease. Hence my comment above about using a grease sparingly. The tolerance is so close for that taper, that too much grease will stop it from coming to gether and it will eventually work loose.
Del, is that what happend???

[fstbttms]

OK, once again I'll have to play the experience card. I have installed many, many props in my 12 years as hull cleaner. Every single one of them was lubricated with waterproof grease. ZERO problems with props loosening up. Further, the argument that the tolerances between prop and shaft are super critical is a fallacious one, IMHO. I maintain that for a prop/shaft combination to have the tolerances that you are describing would require that they be purposely fabricated together. And this is not the case, as we all know. In fact, it is common practice to use a plastic shim to fit a prop to a smaller shaft size. Never a problem that I've seen.

[delmarrey]

Originally Posted by Alan Wheeler

Del, is that what happend???

Yep!
I machined the shaft myself to fit the prop perfectly, if there is such a thing, and I torqued the nut on. Three weeks and 65 motor hours later when the boat was back on the hard I pulled the prop to get some measurements and the prop came off by hand, no puller. The water proof grease was still in there. I'd rather use a puller to get the prop off. At least I know it's on tight. A loose prop can wear the shaft and prop hub.

Yeah! I know what your thinking, you think I did a bad machine job. Not so! When it was dry I could push them together by hand and I wouldn't be able to get them apart by hand. That's why I used the grease.

This last time I didn't use grease and it's doing just fine....................._/)

I have installed many, many props in my 12 years as hull cleaner. Every single one of them was lubricated with waterproof grease. ZERO problems with props loosening up.

Maybe my tolerances were too close. But how often do you get to pull those same props back off??

[Alan Wheeler]

Yeah! I know what your thinking, you think I did a bad machine job.

Absolutley not. I know exactly what you mean. In fact it is proof you did a spot on job. If the tolerance was a fraction out, the grease would simply squeeze out one of the ends and the two metal surfaces would have bound up. But the surfaces would not have been mating properly and would have either worn due to oscillation vibration and/or the prop would have run out. Not teaching YOU to suck eggs ofcourse just readers may be interested.

[fstbttms]

Your experience notwithstanding, it's a fair bet that I have installed, and pulled, at least as many and probably more, props than anybody on this board (and all of them underwater ) I can count the number that have come off without a puller on two fingers, to my recollection. I use grease not to eliminate the need for a puller, but to keep the prop from seizing to the shaft. And I have seen plenty of loose props that were not installed by myself and presumably without grease. And I have seen many more, installed by myself, that have never come loose.

[delmarrey]

Fine!
At least props and shaft's are not ferrous steel to weld themselves together.

I'll submit to the experts with the practical experience. I guess there is something to say about sloppyness in machining. It's hard to break old habits from working on jets..........................._/)

[never monday]

Originally Posted by fstbttms

I maintain that for a prop/shaft combination to have the tolerances that you are describing would require that they be purposely fabricated together. And this is not the case, as we all know. In fact, it is common practice to use a plastic shim to fit a prop to a smaller shaft size. Never a problem that I've seen.

I disagree with this statement.

Props and shafting are machined to an indusrty standard. There for if every reputable shaft and prop builder uses this standard, then all the tapers are the same.
I have no answer for the lube/not lube arguement. I'm in fresh water and my world is different.