Bronze Thru Hulls Causes Saildrive Corrosion?

[Pete7]

Originally Posted by s/v Jedi

This person isn’t qualified to post that but it’s the Internet and fora are just for entertainment so I guess that’s what it is to him.

Nylon thru-hull fittings should never be used below the waterline. Unless your hull is aluminum, you can use a copper based antifouling. No, don’t use it on the sail drive.

Whilst I was reading the nonsense above, I thought Jedi is going to have a fit when he reads this

Sabado, out of curiosity how many through hulls have you got? We are slowly replacing ours with Trudesign from NZ, less the engine intake which sits in the engine space, all bronze including the filter. There was a supply problem in the UK with Trudesign just after Covid, so had to revert to DZR for the heads inlet, but plan to change that next time around.

Your next bit of research will be to decide if you want the bolt through type like Groko, or are happy to have mushroom through hulls like many of the European yachts. Its been discussed at length repeatedly on CF and there are strong opinions on both sides.

Oh and one other minor point, tapered threads are popular in the US add to the complication. We tend use parallel in Europe unless someone has mixed household plumbing items on a boat.

Pete

[Sabado]

Originally Posted by Pete7

Whilst I was reading the nonsense above, I thought Jedi is going to have a fit when he reads this

Sabado, out of curiosity how many through hulls have you got? We are slowly replacing ours with Trudesign from NZ, less the engine intake which sits in the engine space, all bronze including the filter. There was a supply problem in the UK with Trudesign just after Covid, so had to revert to DZR for the heads inlet, but plan to change that next time around.

Your next bit of research will be to decide if you want the bolt through type like Groko, or are happy to have mushroom through hulls like many of the European yachts. Its been discussed at length repeatedly on CF and there are strong opinions on both sides.

Oh and one other minor point, tapered threads are popular in the US add to the complication. We tend use parallel in Europe unless someone has mixed household plumbing items on a boat.

Pete

There were a lot but most were not below the waterline. Twelve were just for the air conditioning. [emoji15]

The parts used by the factory were of poor quality and mismatched.

Tru design wouldn’t fit in all the locations so we chose to go with Groco.

We looked into the bolt through style but in the end we didn’t install them. Our bilge is shallow and we don’t store anything in them so we made the call to use the same type of install as the factory just with better material. Yes, I know, this was a riskier choice but we made it. Perhaps the next refit, we’ll loop back to them.

Here’s some photos of what was removed. Five years old.

[Pete7]

Yuk, still at least the scrap yard would have been happy, oh and the local chandlers

Personally, I a quite happy with mushroom through hulls. The original bronze ones lasted well for 34 years.

[s/v Jedi]

I see a lot of Groco valves, which are perfectly fine when installed on Groco flanged adapters.

Don’t thru-bolt, that old school method is fine for wooden boats but on fiberglass you simply use a G10 backing plate and tap thread in that.

Of course every crazy story has some truths in it, like the stress risers, hard spots caused by backing plates. This is why they need to be round and the edge chamfered with a 45 degree router bit. That last part often not done.

If you put valves directly on top of thru-hull fittings then you replaced a flawed design with the exact same flawed design

[Sabado]

Originally Posted by s/v Jedi

.

If you put valves directly on top of thru-hull fittings then you replaced a flawed design with the exact same flawed design

Absolutely if the only flawed part of the system is the lack of a flange. At our haulout inspection, our bigger concern was the poor material selection that needed to be addressed ASAP and, unfortunately, we could not extend our stay in the yard.

It’s on our (ever increasing) to do list but at least we don’t have crumbling parts.

[Bowdrie]

Originally Posted by s/v Jedi

I see a lot of Groco valves, which are perfectly fine when installed on Groco flanged adapters.
on fiberglass you simply use a G10 backing plate and tap thread in that.

Yes, and with the G10/Groco adaptor one could use a Forespar Marelon thru hull, or whatever,,,.
The style or material of the thru hull becomes a matter of choice.

[Emmalina]

Always amazes me the lack of sea chest/manifolds used in pleasure craft. I will stick with my one through hull thanks.