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post #1 of 3 Old 07-11-2007 Thread Starter
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Replacing thru hull


The surveyor said that I have to replace the thru hulls on my 79 catalina 27 as they have the garden variety gate valve thus I need to use a marine ball valve. To do this I need to also add a vinyl nipple which I posted about before. However when I hauled the boat out last week to do my cutlass bearing I noticed the boat doesn't have the bronze nipples on the out side of the holes. It is just a hole drilled into the hull of the boat no nipple or anything. Is this common for older boats? I looked at an old columbia at the yard and it had the same thing for the thru hull. There was no nipple on the outside just a hole.

If this is the case to install a nipple when swapping the sea cocks do I just drill the hole out bigger since there is no nipple or is there a nipple under the glass in the hull? Sorry if I am not explaining this well. I wish I had taken a picture.
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post #2 of 3 Old 07-11-2007
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The Catalina "thru-hulls" are just bronze pipes glassed into those holes you see from the outside. They should be threaded and the gate valve will unscrew from the pipe and a ball valve will screw on. That is assuming that you can just unscrew the gate valve, which depending on the condition of the pipe and valve, may not be possible.

With that said, since the boat is out of the water, replacing the pipes with real thru-hulls is the right way to do the job, IMHO. In my case, I just used a hole saw the proper size for the new thru-hull and centered it over the old bronze hole and cut it all out in one shot. On another Catalina, to help keep the hole saw centered, I have hammered in a wooded plug (from the outside), cut it off flush, and used a hole saw with a center drill bit in the wooden plug. Good Luck!
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Yes - that is normal on older Catalinas - but not the correct way to make a thru-hull. What Catalina did was just drill out a hole in the hull and then glassed a bronze pipe directly in the hole. Then they built up glass and resin all around the pipe to form what looks like a "volcano". You should really replace all of them on the boat if thats how they were done (I guess your surveyor would have told you that as well). You will need a grinder and if you have a sawzal - use that as well. Cut off the bronze pipe close to the hole as possible and then grind out everything else. You may want to considor using a hole-saw slightly larger than the pipe to drill out the remaining piece glassed in and then install a slightly larger thru-hull fitting. Make sure you create a backing plate out of marine-grade plywood when installing the new one.

I hear its not that big of a job. Do some archive searches in the forum for thru-hull installation - there are lots of posts on the subject. I just replaced one of mine a few weeks ago.
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