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Capnblu 12-05-2012 03:25 PM

Prop shaft material
 
I have a 42' Tayana with a small perkins engine, a 4-108 (25-38 hp), a velvet drive transmission 2:1, and a Walter v drive. This set up spins a 1 1/4" shaft, 7' long, and I am thinking of hanging a Maxprop off the end of it. A PSS shaft seal will be fitted to the inverted stuffing box collar. What do you think would be an appropriate grade of stainless to make the drive shaft out of? The boat will live in the tropics.

Thanks Brian

chef2sail 12-05-2012 06:47 PM

Re: Prop shaft material
 
aquamet 22

Change cutlass and collar at the same time

Capnblu 12-05-2012 07:34 PM

Re: Prop shaft material
 
Is 316 appropriate?

Waltthesalt 12-05-2012 07:43 PM

Re: Prop shaft material
 
The stainless normally used is 304 and at 1 1/4 diameter that should be well strong enough with a safety factor well over three. A more common material is tobin bronze which has about the same yield strength but is more elastic. High strength alloys include Aquamet 22, 18 and 17; Monel 400 and K500 But they're overkill for your situation. more for special situations.

Stumble 12-06-2012 02:25 AM

Re: Prop shaft material
 
I would never recommend any stainless grade for application under water. Obviously I will recommend titanium instead of things like aquamet or bronze, but they would certainly be preferable to stainless.

The issue with stainless is that it has different galvanic potential in and out of the water. So a stainless shaft actually galvanically attacks itself (this is what shaft zincs are for).

copacabana 12-06-2012 04:22 AM

Re: Prop shaft material
 
I once had a 304 stainless shaft corrode and pit so heavily that it had to be changed. It had a zinc on it the whole time. I would think that for the small difference in price it would be better to go with a higher grade of stainless or even monel or titanium.

Stumble 12-06-2012 03:14 PM

Re: Prop shaft material
 
I know for the beneteau 42's shaft we just replaced the price for titanium was about $50 more than the aquamet price he had. And we delivered it with all the machining completed. He figured it was worth it just for the brag factor at the bar :D

aa3jy 12-06-2012 03:27 PM

Re: Prop shaft material
 
Quote:

Originally Posted by Capnblu (Post 957378)
I have a 42' Tayana with a small perkins engine, a 4-108 (25-38 hp), a velvet drive transmission 2:1, and a Walter v drive. This set up spins a 1 1/4" shaft, 7' long, and I am thinking of hanging a Maxprop off the end of it. A PSS shaft seal will be fitted to the inverted stuffing box collar. What do you think would be an appropriate grade of stainless to make the drive shaft out of? The boat will live in the tropics.

Thanks Brian

Monel

Inboard Hardware: Propeller Shafts

..we replaced our 1 1/4" x 10ft with Monel..done by Kastel Bros. in St. Michaels,Md.

One 04-12-2013 12:07 PM

Re: Prop shaft material
 
Old thread, I know, but I wonder what the price difference would be between a bronze (or stainless) shaft and one made from titanium.

And while we're at it, what about a 2 or 3 bladed folding propeller from titanium compared to one made from bronze? I know that those supercavitating ones are often made from titanium, but I'm talking a slow moving one attached to a reasonably light boat and few (<15hp) hp.

I probably won't be able to afford it, but I think it would be great to save a bit of weight down there, while at the same time not having to deal with bronze/brass underwater.

tommays 04-12-2013 01:25 PM

Re: Prop shaft material
 
FWIW my original bronze shaft lasted 42 years and the Stainless one is doing just fine as you do have to be sure of there are certs on on the SS as substandard stuff is the cause of most problems

http://i565.photobucket.com/albums/s...613_133517.jpg
All my underwater hardware is original except the seacocks because they were gate valves

http://i565.photobucket.com/albums/s...1_12110002.jpg

The 42 year old stuff that was changed because I count see sticking the new prop on the 42 year old shaft

http://i565.photobucket.com/albums/s...exfoldprop.jpg

The current flex-o-fold which just kicks azz in reverse

with the amount of bottom paint and other silly stuff I commonly see on props its no wonder stuff happens


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