Replace Thru-hulls?

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Randy K

Our 1986 Catalina 22 has a plastic through-hull for draining the sink. The thru-hull appears to be in good shape but it is now 18 years old. At the next haulout I am thinking of replacing it as a preventative maintenence move. Does this sound wise or unnecessary? Also, the previous owner had a toilet installed (no holding tank, direct flush overboard. Yuk!) which I removed a few years ago. I am considering removing the the toilet water intake thru-hull (brass), beveling out around the hole and then fiberglassing over the hole. Any advice or things to watch out for? Thanks.
 
Jun 5, 2004
97
- - Greenwich, CT
C-22 Thru Hulls

I read somewhere, on this list I think, that someone had one of those “plastic” thru hulls for the sink drain and discovered that it cracked and was leaking. So I guess it would be advisable for you to change that thru hull. However, I would use a bronze thru hull with a Marelon ball valve. However, there are people who do not like the Marelon valves as they have a tendency to have their handles break off. However, with proper seasonal greasing, they should operate faultlessly for many years as mine have for twelve years. A second issue is that many of the small ½ inch to 3/4 inch vales are brass and not bronze. Placing a brass valve onto a bronze thru hull is a recipe for disaster in that the electrolysis that sets up between the brass and the bronze will destroy the brass valve which will then fail and leak badly into the boat. Marlon on the other hand has no electrolysis complications with bronze thru hulls and hence is a better selection over a metal valve in that you cannot be sure if the metal valve is really bronze or actually brass with in incorrect label of bronze placed onto it. The intake for the toilet is probably best just left alone, as they say, if it an’t broke, don’t fix it. Holding tanks are still a viable option on a C-22, and while such may not be to your particular needs, it may be important to a respective purchaser of your vessel in the future.
 
Feb 13, 2004
63
Oday 22 Setauket, NY
At least inspect them

If you don't replace your plastic through hulls, at least inspect them carefully. UV rays damage plastic, and modern UV protection was not available for plastic years ago. I have had experience with plastic through hulls that looked OK, but a closer inspection revealed major cracks. Try to rotate them and look for crack. But at 18 years of service I would just replace them. Also, I would choose Marelon fittings as replacements. Marelon is glass-reinforced plastic that is stong, minimally affected by sunlight, and has no chance of galvantic corrosion. Then you can use whatever type of seacock you want. Brad
 
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