BruceinBangkok wrote:

I suspect that the "marelon" was a reference to the valves, but in
any case there have been various warnings not to use plastic for thru
hull fittings as they deteriorate in sunlight.

My own preference for thru hull use is bronze for the actual fitting
and bronze, if possible, for the valve. I can buy here, bronze ball
valves that are lower in price then the normal "sea cocks" and last
well.
Cheers,

Bruce

While I agree about the plastic through hull fitting, please be cautious
with the ball valve. The valve part is fine, but the threads are
usually a tapered pipe thread and do not actually make a solid coupling
to the bronze through hull. With little provocation it may break off
the two threads that it is actually engaged. DTBT and see several a
season.

Matt