Prop shaft

[nutcase]

I need to make a new prop shaft. My current one is 7/8" bronze. I'm thinking to replace it with 7/8" 316SS. It's cheaper than bronze and, when I looked at bronze, the number of different types was overwhelming - I was surprised. I was planning on buying the shaft and having the prop thread and slot machined into it.

Some questions:

1. Do I need to buy ground rod?
2. Does anyone know the tolerance on the diameter?
3. Any reason why this material is not suitable?

Thanks,

Mike

[Don Moyer]

Mike,

I once had a prop shaft made using 316" SS, and it worked very well for 6 or 7 years, at which time I sold the boat.

I'm not aware of any special tolerances that apply to prop shafts, nor am I familiar with the term "ground rod".

Don

[nutcase]

Thanks for your reply. Ground rod just means that the rod is precision ground so that the tolerance is very tight on the diameter (usually +/_ .0005" for a 7/8 rod if my memory serves me correctly). Based on your experience, I think I'll go with that material.

Mike

[dtinder]

Our prop shop only uses stainless----unless they are cutting down a used shaft. 316ss is fine----304 or 305ss (the stuff that bleeds) might be out there. There are more expensive shaft mat'ls avail but not worth the extra bucks in my mind. Re tolerances: I'm not familiar with "ground rod" either---but any prop shop should know the taper (I think 1/8 or 1/12)----as these are the guys that bore the tapered hole in the prop----which is supposedly "std" in the industry. Be cautioned about European sizes as they don't go by the same book as we do. Some even use metric on some dia'ms.
Best,

[Don Moyer]

Mike,

Thanks for the explanation. Good luck with your new shaft.

Don

[hd78half]

Fast becoming a standard for prop materials is Aquamet, a stainless alloy with superior corrosion resistance to SS304 or 316.

You can purchase a prop ready made from Marine Machining and Manufacturing in Clinton MI, 586-791-8800. Ask for Michelle. The price quoted for a new shaft, completely machined with taper, threads for jamb nuts, hole for cotter pin, and two keyways, overall length of 32", for my sailboat was $213.00. Typical delivery time is 5 - 7 days.

Bronze, specifically K-monel 400 or 500 alloys are not subject to the crevice corrosion that plagues stainless. Some sources say that sacrificial anodes are not necessary with bronze as they are with SS. Bronze does not have the same resistance to torsional deflection (twisting) under high loads that SS alloys have but this is not an issue with an A-4.

I'm actually looking for a bronze shaft for my boat. If anyone reading this posts knows of a source, please let me know.

Thanks,
Al
920-265-0941

[Don Moyer]

I'm quite sure the machine shop that has made several stainless prop shafts for us (Nye Machine and Design) can order bronze. You can call them at
(717) 533-9514.

Don