Composite thru hulls: good or bad idea ?

[Mambo42]

By coincidence I stumbled on 2 videos this last week talking about the benefits of composite thru hulls. There is a brand called Trudesign, they are from New Zealand and they apparently specialize in these thru hulls.
Since the are composite they don't corrode and since some of my thru hulls don't look in such good condition anymore (boat is 45 years old) I am thinking of changing those into composite thru hulls. The ones that are still good I will simply keep as they are.

Does anyone have experience with composite thru hulls ? Are they really so much better ? Is there a negative side to it as well or is it just a positive innovation all around ?

 

[rslifkin]

I use the composite Marelon thru hulls pretty much everywhere above the waterline. I stick to brass below the waterline though, as I've heard mixed reviews on the composite valves (as far as issues with sticking) and I wouldn't want to put a metal seacock on a composite thru hull. Plus, properly installed and maintained bronze parts can easily last 30+ years below the waterline, so needing to replace them probably once in the boat's life isn't a big deal in my mind.

 

[heysteve]

I had Forespar Marelon seacocks on a previous boat that was 18 years old. They looked good as new and worked fine.

 

[Mambo42]

I use the composite Marelon thru hulls pretty much everywhere above the waterline. I stick to brass below the waterline though, as I've heard mixed reviews on the composite valves (as far as issues with sticking) and I wouldn't want to put a metal seacock on a composite thru hull. Plus, properly installed and maintained bronze parts can easily last 30+ years below the waterline, so needing to replace them probably once in the boat's life isn't a big deal in my mind.

Most of them are still good, but some, difficult to reach valves, don't function anymore. That means this winter I will have to get to them when the boat is out of the water and most likely I will have to take them out anyway. I can either go with brass again or go for composite.
Composite seems to be much easier to install, but I have no experience with them as underwater thru hull. I have see the composite thru hull of my old depth meter, that one was not completely intact anymore. I have changed that one for a new one, but if that will happen in a few years to new composite thru hulls, it is something to think about.

 

[C lectric]

2 or so years ago I was required to remove all my Nylon through hulls and replace them with bronze units. Reasoning was they were to low and on the hull sides so subject to being broken by a wayward log. Hard to argue with both insurance co. and the surveyor.
I was a wee bit annoyed as it was a LOT of work and a fair bit of expense but it was done.
What really put me off is I took a couple of the original through hulls and smacked them solidly with a sledge hammer. They flew but did not break or crack .

The boat was launched in 1,977 and is now 47 years old.

Oh well, sometimes you can't win.

 

[lwarden]

I have all Marelon thru hulls on my boat and they are original (22 years). They all operate perfectly and when I added a new one for a dedicated raw water washdown I used the same type. I'm more worried about de-zincification of bronze over that period of time than I would be any issue with the Marelon ones.