Thru Hull replacement

[pzmaria]

Hello there, I'm replacing all vinyl thru hull fittings above the water with 316 stainless. I have a question regarding exhaust fitting as it sits just above the water line. Can I still put 316 stainless or should I go bronze there? I would prefer stainless. Thanks all for any input.

pzmaria

[deblen]

Good info on thru hulls here: https://marinehowto.com/

[Statistical]

Most people prefer bronze or marine grade composites below the waterline (to include any thruhulls which could go under waterline due to heel) but Groco does make 316 Stainless Steel seacocks and thruhulls.

Note if you use a SS thruhull then you should also use a SS seacock. Don't mix metals. Exhaust may not have a seacock but just thought I would mention it just in case.

[Matt Johnson]

A through hull is fine in stainless if above the waterline.

[SailingHarmonie]

Stainless exhaust thru hulls will, even if of the best grades of stainless, weep a bit of rust down the hull. If that bothers you, then bronze, is might be the better choice. If you really like the silver shine, you can use chrome plated bronze and have the best of both worlds.

[hlev00]

Originally Posted by SailingHarmonie

Stainless exhaust thru hulls will, even if of the best grades of stainless, weep a bit of rust down the hull. If that bothers you, then bronze, is might be the better choice. If you really like the silver shine, you can use chrome plated bronze and have the best of both worlds.

I can confirm the rust stains from "stainless" on the exhaust.

[s/v Jedi]

Everyone does whatever they want, but I can explain the choices made aboard s/v Jedi:

The exhaust is a Centek fiberglass exhaust pipe glassed in the transom. On the outside, one of those black rubber flapper thingies is mounted on the stub to prevent ingress of water when waves slap the transom.

All other above water thru-hulls are Forespar Marelon. Zero maintenance and zero issues is tough to beat

[bstreep]

Personally, I’d choose bronze or Marelon over stainless. Stainless doesn’t belong below the waterline.

[capt jgw]

Originally Posted by hlev00

I can confirm the rust stains from "stainless" on the exhaust.

Yea, it's stain "less", not stain "not at all". Lots of acid and other nasty stuff in engine exhaust, they will rust a little. I wouldn't trust Marelon with the heat, so bronze is the choice. Chromed if you want it shiny.

[capt jgw]

Originally Posted by bstreep

Personally, I’d choose bronze or Marelon over stainless. Stainless doesn’t belong below the waterline.

Correct. Stainless, even 316 alloy, is exactly the wrong material for most of the stuff they use it for. It's fine for handrails and things, but not anything structural like keel bolts and the like. Unfortunately most builders use it for those things. Galvanized steel is better, bronze is best.

[s/v Jedi]

The Centek fiberglass fittings for exhaust are the best option and are simply epoxied in so no leaks ever.

https://centekmarine.com/wp-content/...Data-Sheet.pdf

[Bowdrie]

Originally Posted by s/v Jedi

The Centek fiberglass fittings for exhaust are the best option and are simply epoxied in so no leaks ever.

^ Not to mention the vast range of general plumbing issues that can be solved with them, lots of other uses too.
A perusal of their catalog whilst letting your mind wander you can come-up with all kinds of applications.
Expensive? Yes, but they last forever.