Stainless steel for a P bracket?

[iainbluk]

Anyone know if this is a good idea? I am a part owner in a Jeaneau 40 in Greece and recently we picked up a rope with a piece of wood attached which caught the prop, and damaged both the propshaft and the prop as well as the p bracket. A replacement bracket is being made in stainless, but one of the other owners suggested 'that it might not be a good idea as stainless was not particularly well suited to continuous salt water immersion'. The original is made in brass I think.

 

[rogerthebodger]

I consider stainless below the waterline to be OK if it is 316 others don't. Your current should not be brass but most likely bronze.

I have a steel boat and moat of my sea cocks are 316 stainless steel.

 

[Tranona]

The original will have been a bronze of some sort with rubber cutless bearing. Best to replace it with exactly the same. Stainless is sometimes used, but it is usually cast rather than fabricated as I suspect yours will be. The potential problem with stainless is crevice corrosion, particularly around the weld that will attach the tube to the bracket and inside the tube in the interface with the brass shell of the bearing. The potential corrosion there can be reduced by using a phenolic shell bearing or a composite.

Overall, though best to stick with the original equipment - and fit a proper rope cutter to reduce the chance of similar damage in the future.

 

[30boat]

In theory stainless can be susceptible to corrosion where there's still water and lack of oxygen but I believe it would work in practice.The main problem area could be where it enters the hull as there'll be water and little or no oxigen there.

 

[Pasarell]

I agree with 30Boat. The most vulnerable area to crevice corrosion will be where the P bracket is attached to the hull. Over time the sealant will allow some water in and crevice corrosion is most likely to occur where the water is static and no oxygen present. Crevice corrosion is probably not such a big problem as some people fear, however, it is very difficult to detect so when it does occur the item will fail catastrophically without warning. I would use bronze given the choice