[Kymasabe]

I'll be replacing the transom on my little 12 foot aluminum boat soon, as slowly gathering all the material I'm going to need and was planning on picking up the bolts/nuts/washers this week but thought of a potential problem. Will stainless steel bolts and washers be a problem thru the aluminum and on the outside of the boat. Will the stainless washer react with the aluminum? I will be sealing everything with 5200 or possibly 4200 so that might insulate one metal from the other, though I doubt it. I considered rubber washers but thought they'd eventually compress, causing the bolts to loosen and possibly egg the holes thru the aluminum.
Or...am I worrying unnecessarily and stainless thru aluminum and washered agasint aluminum will be fine?
Is there such a thing as an aluminum washer and should I use one?
Also...exterior...should I use standard size washers or fender washers?

[tashasdaddy]

i use fender then standard on top of the fender.

[Tim Frank]

I am facing the same thing.
The original bolts on my transom were aluminum, and there is enough separation between stainless and aluminum on the metal activity chart that I think that staying with aluninum is the way to go.
They are available from any good fastener shop. The place I got them had to special order, but they arrived in two days.
They are also available on-line.

I am not familiaer with 5200 or 4200 sealer. What are they?

[tmcalavy]

Marine sealants...available at Wally World and other places.