Prop Shaft Material

[exapp]

Hello,

Need to have a new 25mm prop shaft made.

What material should I be using...ie what grade of stainless steel??

Regards,

Exapp

 

[cliff]

What was the old one made off?

Failing that 316 is a good bet or if you want to go up market go for a duplex stainless (2205?)

Duplex stainless steels generally have similar corrosion resistance to austenitic alloys except they typically have better stress corrosion cracking resistance. Duplex stainless steels also generally have greater tensile and yield strengths, but poorer toughness than austenitic stainless steels so my money would be on 316 grade.

An alternative would be Monel 400 or even Monel K-500, but now you are talking a serious number of beer tokens.
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"Artificial intelligence is no match for natural stupidity"
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[boatmike]

Can't argue with any of that, agree with Cliff entirely but would add that the higher cost alloys are generally called for if the propshaft is enclosed in a waterfilled outer tube or is in some way surrounded by water that cannot circulate. The enemy is crevice corrosion caused by micro-electrolytic action in a de-oxygenated environment. If there is circulation of water around the area as there would be if the shaft is for instance supported by a P bracket with a Cutless bearing then 316 is probably OK. A good indication would be if you have any corrosion or pitting on your existing shaft. If you don't and the reason for a new one is that the existing one is worn or bent then 316 is probably OK. More information on the type of set up and type of boat and the reason for replacement would help.

 

[cliff]

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"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>