All were "big nut" thru-hulls with gate valves. I replaced them with
brass NPT ball valves, which I service yearly and I have double SS
clamps everywhere. No problems whatsoever. If I were in salt water, I
would act differently.


Why? Do boats not sink in fresh water or something

I do not disdain the arguments, but like you, I have confidence that
these buggers are NOT coming off and are much safer than the original
gate valves. Also I have plugs tied to each thru hull, which I don't
see a lot of here on Lake Ontario, even though that is a "standard
precaution" as well.


The issue is less of gate valve vs ball valve, than it is NPT vs flange
and one of corrosion. Nowadays common cheapo hardware store grade valves
are far more corrosion resistant than anything from years ago (except
possibly the super-expensive Monel sea cocks, which I've seen exactly
once in a lifetime).

A sea cock should (in theory) be supported by a flange, not just screwed
onto a protruding pipe. There are lots of ways... including just plain
heeling... that the pipe & valve come under strain. Still, with modern
materials and good attention to detail (btw it is possible to
overtighten NPT connections & split the casting or collapse the pipe
wall) it should be just fine.



engsol wrote:
When I bought my boat, I gritted my teeth and removed every thru-hull,
each had a gate valve. Oddly enough, my pre-purchase surveyor didn't
see a thing wrong with gate valves...but he dinged the boat for not having
PFDs aboard. A boat needs PFDs aboard when it's on the hard?


LOL but he presumed you were going sailing some day!

Issues with gate valves... at one point they were considered acceptable,
every mass-produced boat had them. In the old days, plug valves were
considered preferable... especially if made of Monel.


I've been aboard a number of boats where the owner has the tapered
plugs neatly stored in a locker (he'll remember which one any minute now).
To me..a novice,.. it makes sense to have the proper plug co-located
with the thru-hull. I wonder why so many boat owners don't.

It's just one more thing. Lots of the boats I go on have tapered wooden
plugs tied with yard around the base of the thru hull... a nice
precaution... but frankly I'd have more faith in a plastic baggy & some
duct tape.

How many people have removed seacocks & thru-hulls entirely, and
fiberglassed over the hole?

http://community.webshots.com/photo/...73346002sUSTvu

This is one way to absolutely, positively, guarantee that it won't ever
leak! But you have to be sure that you don't want whatever system it
supplied seawater to. In this case, it was the seawater inlet for the
head which I tied in to the seawater circuit for the A/C... not
satisfactory really. It was a case of connecting too many things to one
valve & strainer, and the A/C pump kept losing it's prime until I
installed a check valve (highly not recommended). But we're installing a
FW flush head this spring.

Fresh Breezes- Doug King

On Thu, 21 Apr 2005 14:26:51 -0400, DSK wrote:

All were "big nut" thru-hulls with gate valves. I replaced them with
brass NPT ball valves, which I service yearly and I have double SS
clamps everywhere. No problems whatsoever. If I were in salt water, I
would act differently.


Why? Do boats not sink in fresh water or something

Sure they do, but sal****er eventually dissolves brass fittings,
meaning they are a no-no in even brackish water.. "Proper" seacocks
are salt-resistant bronze, or these days, Marelon. In fresh water, you
can use brass plumbing ball valves...at about 1/4-1/8 the price of
bronze. The actual thru-hulls are still bronze: it's the cocks screwed
onto them that are brass, with teflon tape and thread sealer between.




The issue is less of gate valve vs ball valve, than it is NPT vs flange
and one of corrosion. Nowadays common cheapo hardware store grade valves
are far more corrosion resistant than anything from years ago (except
possibly the super-expensive Monel sea cocks, which I've seen exactly
once in a lifetime).

A sea cock should (in theory) be supported by a flange, not just screwed
onto a protruding pipe. There are lots of ways... including just plain
heeling... that the pipe & valve come under strain. Still, with modern
materials and good attention to detail (btw it is possible to
overtighten NPT connections & split the casting or collapse the pipe
wall) it should be just fine.

I have been careful with the hoses and whatnot to avoid lateral
forces. I suppose if the engine came loose and slammed into the ball
valve at speed, I'd be in trouble, but that could easily tear a hole
in the actual hull, meaning I have bigger issues.

R.