HELP White crud on my thru hull

[arch007]

I have thi white crud on my thruhull.


What is it ?


Thanks,


jim

[s/v Jedi]

Taste it to check if it’s salt accumulation.

That is not a proper setup, looks like they screwed a valve on a thruhull fitting. This doesn’t work well because the threads are different. I recommend you change that and any others like it. Read about the Groco flanged adapters which accept a linear thread from the thruhull fitting and present a tapered thread for the valve, while having a flange for proper mounting. MarineHowto.com has the why and how on this

[stormalong]

If it is hard and rubbery it is caulk. Often the squeeze out from installing a through hull fitting is smoothed over on the inside.

If it is powdery it is the result of galvonic corrosion. Which means that your through hull may be the wrong alloy. Proper bronze will just turn green

If it is greasy it is seacock grease. That would be my last choice but it is a possibility.

[arch007]

Thanks.


That other trhru hull is for the water cooled Isotherm thru hull.


That is what they provided.


I agree. Does not look very strong. Not all that keen on the isotherm water cooled thru hull. Worried it will corrode if you dont replace the zincs.


I was working with the isoterm fridge as it was never on before. So maybe the isotherm is connected to the thruhull and corroding all the thru hulls ??????

[arch007]

Not caulk.


Just happened very recently.


When I was fooling with the isotherm fridge. It is water cooled and the isotherm thruhull is the one next to the groco thru hull.


My feeling is the isotherm which was never turned on did this when I started it.


If so is the corrosion very bad or can I just wipe it off. Do I need replace the thruhulls !!!!!!!


Have turned fridge off.


Going to wipe it off and see if it returns.


jim

[s/v Jedi]

Are you on shore power? If so, do you have a galvanic isolator or isolation transformer?

[arch007]

no.

but this happened in the last 3 weeks when I started working on the isotherm.

before it was ok.

the crud was well within the last 3 weeks.

[Sailmonkey]

Have you been running heat or in any other way been drying an area that has always been damp previously?

[Pete7]

Originally Posted by arch007

If so is the corrosion very bad or can I just wipe it off. Do I need replace the thruhulls !!!!!!!

Jim, Nick (SV Jedi) has raised a number of concerns. One of which is in the US they use fittings which have a tapered thread. Use one of these to join a parallel thread through hull provides a weak join and is a very bad practise. However, in Europe we tend to use British Standard Pipe (BSP) parallel threads for valves and through hulls which is completely different. That said it would be useful for you to dismantle and confirm what you have.

I notice a nut from the handle on the top left valve has fallen off, the valve shaft looks rusty and it may not be DZR or bronze inside, instead a cheap brass valve which has to go.

There appears to be a wire going to the groko seacock, but not the other seacock top left. Again, in the US they connect underwater fittings to the anode. European yachts tend to have all underwater fitting un-bonded. Both ideas are correct but you ought to chose one or the other.

Are you planning to lift out in the next couple of months?

Have a good read of this, written by another forum member, Mainesail:

https://marinehowto.com/seacock-thru-hull-primer/