Bronze thruhulls in topsides?

[Saltyhog]

As part of our extensive refit, we're replacing all of the thruhulls and seacocks. From the factory, most of the above waterline thruhulls were white nylon. I'd like to replace them with something more substantial, and as some of them are under water when on heel, I also plan to add seacocks. My plan had been to use bronze for all thruhulls / seacocks, both above and below the waterline. Our boat has traditional lines, so the bronze would fit the boat aesthetically. A dock-mate has warned off this plan as he thinks the bronze will leave green stains below them. As I'm also having the topsides painted, I would rather not have the staining. Is this a real potential issue, or can any potential staining be avoided or easily dealt with.

[Cheechako]

I've not noticed a lot of green staining transferred tot he hull on boats with bronze hardware. Anything is possible I suppose. There are chromed bronze mushroom fittings if you desire. Definitely get rid of those white fittings, i've seen them jut snap right off after UV exposure.

[Saltyhog]

Originally Posted by Cheechako

I've not noticed a lot of green staining transferred tot he hull on boats with bronze hardware. Anything is possible I suppose. There are chromed bronze mushroom fittings if you desire. Definitely get rid of those white fittings, i've seen them jut snap right off after UV exposure.

Thanks. I've not had good luck with chrome plated bronze. It seems that no matter what, it will peel and wear in 5-10 years. I'd rather see the patina-ed bronze than peeling chrome. I think the choice above the WL is either stainless or bronze. I'd prefer bronze unless the staining on the painted topsides is going to be obnoxious.

[Cheechako]

Yeah. Perhaps perusing the marina for traditional boats , Hans Christian etc will tell the story. I dont think I've noticed it around portholes etc.

[moctrams]

These work the best. A little expensive.

Bronze and Stainless Marine Hardware - Spartan Marine Hardware and Accessories

[HopCar]

Any above the waterline discharge, bilge / Air conditioner, can leave a streak down the hull. A way to avoid the streak is to use flush mount thru-hull fittings but don't flush mount them.
https://www.groco.net/products/fitti...es-flush-mount

Don't taper the hole. Let them stand proud of the hull. This gives a drip edge that causes the discharge water to fall free of the hull instead of running down it.

[KadeyKrogen38]

Paint them same as topsides, I did no issues.

[JOHNMARDALL]

Another possibility is Marelon, a composite plastic. It's quite expensive, but is well regarded and is not subject to corrosion. If any of the readers have had a bad experience with Marelon, I'd like to hear about it - I'm replacing the through hulls on boat now.
Thanks

John Mardall
Vetus Maxwell Group

[gbr]

Or the thru hulls from TruDesign - UV resistant and bloody strong.

Skin Fittings Threaded | TRUDESIGN

[Offshore1960]

Go with bronze, you will never have to worry about them again. That's what I did on my Bristol 40 that I'm re fitting now. And as a previous poster mentioned the plastic ones get brittle after UV exposure.

[Shrew]

Originally Posted by Offshore1960

And as a previous poster mentioned the plastic ones get brittle after UV exposure.

To be clear, there are Nylon and Marelon through-hulls in the generic 'plastic' category. Nylon corrode over time and bcome brittle as a result of UV exposure. Marelon DO NOT.

[four winds]

My forty year old boat has several original and a couple added bronze throughhulls above the waterline that do not show any staining from the bronze.

[buzzstar]

There are definite differences among alloys. Quality marine grade bronze alloys should last a lifetime. Watch out, pay attention, and do some research. Not all bronze is marine grade, and sometimes supposed bronze is technically brass. I do not think you will get green stains from marine grade bronze, although I admit I somehow recall green patina on items that I believed were bronze.

[bsurvey]

Marelon is all you need to know