Back in 2005 the handle broke on the Marelon thru-hull on the head
intake. I asked on Listserv if it would be better to replace the
"plastic" through-hull fittings with something more substantial, like
bronze. I thought it would be a smart move.
I saw both stainless steel and bronze alternatives in the catalog for
less money than the original Marelon. Jon Ayers gave me my answer
when he said "Marelon is chemically inert in salt water, and is the
most tolerant of poor maintenance...Bronze is subject to galvanic
corrosion, and requires regular maintenance."
More recently, on Jun 14, 2010, at 12:35 PM, Jamie Morrison wrote:
I guess this would bring up the discussion of which is better, Marelon or bronze. When I bought my boat it was equipped with all Marelon thru hulls and valves. I thought this was a good thing. Is there a deep dark secret out there about Marelon that should make me think about switching to bronze?
Jon Fitch answered: "Marelon seacocks meet USCG and ABYC
requirements for thru hulls, which are fairly rigorous: they must
withstand a 500 pound load applied the worst direction to the end of
the tailpipe. However Hinterhoeller did not use Marelon seacocks, they
used Marelon thru hulls with a Marelon valve screwed onto them. This
is not (and as far as I know was never) a USCG or ABYC approved
arrangement. The seacocks have a large flange at the base and secure
to the hull with three bolts independently of the thru hull fitting.
The Marelon flanged seacocks still meet the requirements, even though
Forespar no longer files the necessary paperwork for official
approval.
"I replaced all the thru hulls and valves on mine with like, because
the older valves were getting hard to turn and have a weaker stem than
the newer ones. I clamped one of the old ones in a fixture and broke
it off with a hammer to see how hard it was. It took a reasonable
wallop, but less than a bronze one of similar size. On the other hand
a corroded "bronze" one will crumble in your hand. I say "bronze"
because it is nearly impossible to tell what the fitting you are
buying is made from, short of sending it to a lab. Many have a high
percentage of zinc, which I would call brass.
"In my mind the best fix would be to remove the thru hulls and replace
them with a proper Marelon seacock. These don't corrode, are quite
strong, and if you smear a little teflon grease on them once a year
before launch (can be done with a Q-tip from the outside without
disassembly) will last nearly forever.
"On the other hand, I haven't heard of a single Nonsuch sinking due to
the failure of the original installation, so it is probably much ado
about nothing."
Jon Fitch
'Anomaly'
Now I realize that both Pete Peterson and John Newell sail mostly in
fresh water, so the salt-water corrosion problem may be less of a
concern to them. Still, there is more of a potential for corrosion
with metals than with Marelon.
Bill Spencer
LIONHEART, NS30U #352 Hyde Park, NY