underwater nuts and bolts

[SteveC]

For permanent underwater skin fittings, rudder shaft and the like what nuts and bolts should be used? Hull and rudder are steel. What would you recommend if anything for overpainting?
Thanks

 

[Guest]

If the skin fittings are bronze I would use bronze bolts as they are more corrosion resistant than stainless underwater and you remove a source of electrolosis. Could you use some form of gaskit to insulate the fitting from the hull rather than relying on paint to stop electrollisis from hull to fitting? Other option I have seen is to weld a steel tube direct to the hull instead of using bolt on fittings then there are no fastenings to corrode?

Roly, Voya Con Dios, Glasson, Lancaster

 

[SteveC]

Roland, it's not the electrolysis side of things I'm concerned about, the skin fittings I'm using are Marelon plastic and as you rightly say stainless should not be used permanently immersed so do I use common or garden steel ?

 

[Guest]

If they are going to be over-painted I would use stainless A2 grade. Our Club boats have these fitted to the outboard cutlass bearing housing and after 14 years were still using the same nuts and bolts.