galvanic reaction?

Polspear · 16 March 2015, 00:45

Hi guys,
Following some examples on this forum I've put stainless steel as transom reinforcement:

Looks more elegant than rottening ply. But it struck me just now: Will it not create galvanic reaction between plate and aluminum engine (prop)? in this case the engine material would be consumed quicker!!! am I right?

Nos4r2 · 16 March 2015, 00:50

Not if you've got good anodes

Polspear · 16 March 2015, 01:05

well... that's the thing: I dont.

Poly · 16 March 2015, 09:10

Quote:

Originally Posted by Polspear

well... that's the thing: I dont.

Well you need to fix that anyway!

You can only get galvanic corrosion if the two metals are both "electrically" connected and immersed in the water (electrolyte). Does the plate sit in the water at rest? Generally two different bare metals touching in a Salt water environment is bad news if you want to be able to separate them in the future so if that is a risk you may want some sort of insulating barrier between them.

Nos4r2 · 16 March 2015, 09:28

Quote:

Originally Posted by Polspear

well... that's the thing: I dont.

You have no trim tab or any other anodes on your outboard?

Max... · 16 March 2015, 09:39

You're probably better off with a piece of decent ply protected against the elements (colour matched too) - should last a few years at least. I cannot see how a thin sheet of SS adds any reinforcement but it does not look great, has the galvanic issues, is slippery and the engine mounts will not bite in very well.

Searider · 16 March 2015, 10:41

Yes, the aluminium of the outboard will corrode in preference to the stainless. Anodes will mitigate this but will be consumed much more quickly.

If the boat is not kept afloat it isn't an issue. If it is, it is.

Plywood pad for me every time. Or a nylon / plastic board.

Polspear · 16 March 2015, 15:47

Thanks guys,

Quote:

You have no trim tab or any other anodes on your outboard?

I am not a professional in this but i do not see anything that could do the job.
Luckily the boat is not going to be kept on water. I wish I haven't realized that earlier. I really don't feel like taking the engine off now. Maybe after the season...
A1an I was hoping to hear your opinion, I know you had exactly the same arrangement on yours, did you have any problems?
cheers

Searider · 16 March 2015, 20:43

There will be anodes on the engine. Probably one on the bracket and one under the cavitation plate. Little grey things. One might look like a tiny fin - that will be the trim tab - to reduce steering loads.

Polspear · 17 March 2015, 21:01

Quote:

One might look like a tiny fin - that will be the trim tab

Yes i've got this one, nothing on the transom bracket though.

jyasaki · 18 March 2015, 20:49

Bracket anodes may be rectangular blocks, often screwed into recesses; or in the case of some Yam's a large handle-looking thing. I would think there'd be something there, as the bracket is somewhat insulated from the motor proper by grease. Make sure the prior owner hasn't painted over it (and replace it if he did.)

jky

Portholme · 19 March 2015, 21:18

I had a stainless transom on one of my boats. It looked great but the galvanic activity was hair raising. Anodes woukd disappear in less than a year.

beamishken · 20 March 2015, 00:45

Quote:

Originally Posted by Polspear

Luckily the boat is not going to be kept on water.

Not a problem if the boat isn't kept in the water you need the water to complete the circuit

cptsideways · 05 April 2015, 21:03

I had a neat engineered plastic 12mm backing plate on my old boat, very neat & would cure the problem with ease.