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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

To-hull or thru-hull?

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smp817
1st Mate

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USA
30 Posts

Initially Posted - 05/18/2004 : 11:48:31

I put my boat in the water yesterday and found a leak in the forward thru-hull. Pulled out and resealed the ball valve to nipple connection and dropped back in, only to find it was still leaking. I suspect the nipple which appears to be cross-threaded into the thru-hull is the culprit, but in reading up on the subject I am wondering about the to-hull vs. thru-hull issue. I have an '89 WK TR Mark IV w/Diesel inboard. Does anyone know if I would have the infamous to-hulls? There is no protrusion on the hull. The thru-hull did not leak last season, but I replaced all of the hoses over the winter, removed the ball valve and may have caused the cross-threaded nipple to loosen. With the boat 40 min. away, does anyone know the size of the forward thru-hull nipple? I think it is 3/4" x 2", but I didn't get it measured last night.
Steve Perry
#5883 "Love & Luck"

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Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 05/18/2004 : 18:17:44

The Catalina to hull consists of a hole drilled in the hull. A streight section of pipe is inserted into the hole and a bunch of fiberglas is piled up around it inside the hull. It kinf of looks like its alias a volcano. The tipical through hull will have a flange on the outside of the hull with a threaded tube going through the hull. Then a flange or flat nut on the inside and having been sealed both under the outer flange and inner nut.

to hull

through hull

last picture is the reason to change

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 05/18/2004 : 21:55:57

The chances of a 1989 having to-hulls are nil.

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smp817
1st Mate

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USA
30 Posts

Response Posted - 05/19/2004 : 10:10:19

Doug, Thanks for the information. It turns out that what I thought was a threaded nipple was actually the top of the plastic thru-hull fitting. When I was replacing the hoses I must have twisted the thru-hull and broke loose the sealant. I am going to replace and reseal the thru-hull, but what will keep this from happening again? There is nothing to keep the thru-hull fitting from twisting in the sealant other than using a glue-type sealant. A nut tightens down on the threaded thru-hull on the inside. How can I tighten the nut down without twisting the thru-hull in the fresh sealant? It seems like a system bound to fail. Any suggestions out there?
Steve Perry
#5883, "Love & Luck"

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 05/19/2004 : 11:59:57

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by smp817
 I am going to replace and reseal the thru-hull, but what will keep this from happening again?
Simply slit the hose lengthwise and pull, not twist. As infrequently as you will need to replace hoses it may not hurt to reseal the thru-hulls at the same time.

How can I tighten the nut down without twisting the thru-hull in the fresh sealant?
The correct way to use a product like Life-Caulk is to tighten the fittings to only about 90% initially, let the caulk cure then tighten to about 95% (obviously if you tighten to 100% you'd squeeze out most of the caulk.) Having the fittings spin in the fresh caulk won't impede the sealant from doing its job after it has cured.

Good luck!
<hr height="1" noshade id="quote"></blockquote id="quote">

Edited by - OJ on 05/19/2004 12:01:02

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 05/19/2004 : 20:11:45

"It seems like a system bound to fail"

No worries, tens of thousands of thru-hulls like this are in use.

To tighten the nut you can have somebody hold onto the outside of the thru hull with a pair of channel locks. I tightened one by myself using a pair of channel locks GENTLY gripping the thru hull.. the handles held together with a nylon tie-wrap... used some twine like to tie it off to the trailer.

Working on a boat by yourself is a true mother of invention.

Remember that the sealant does most of the work. The thru-hull nut doesn't have to be yarded on with a big wrench. Just 'nice and snug', let the sealant set and then snug up a little more.

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ronrryan
Admiral

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USA
561 Posts

Response Posted - 05/19/2004 : 22:31:29

Some throughhulls have a pair of opposed slots on the outside flange fitting; some have a pair of raised studs; both are supposed to help mr. outside hold the threaded thruhull steady whilst mr. inside tightens the nut. A proper installation also calls for a backing pad epoxied on the hull inside, so the inside nut isnt tightening down onto the hull itself, but many people omit this, due to time, materials availability, etc. Life is not perfect and opften neither is thruhull replacement. Ron srsk Orion SW FL

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Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 05/20/2004 : 13:31:14

When installing a through hull apply sealant to the outside and inside of the through hull. Snug the inner nut down to just about finger tight and let it set for one or two days. Use a wooden bung or something similar on the outside to hold the fitting. The two notch device is usually inside the opening. Snug the inner nut down but ((((NOT)))) to tight. Let the sealant do its work not the fitting. I.E. the seal is made by the sealant not the fitting. If you tighten to much and squeez out to much sealant you may create a path for a leak between the fitting and hull where sealant has been squeezed out competely.

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/20/2004 : 14:03:35

When installing a thru-hull, I would suggest doing a dry install first to be sure that both the outer and inner surfaces of the thru-hull lie flush to both surfaces. I had to fabricate a circular wedge for a thru-hull to even out the surface so it could lie flat.

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takokichi
Captain

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USA
321 Posts

Response Posted - 05/20/2004 : 15:10:39

When I replaced the transducers for my depth and speed instruments I discovered that they had been installed with NO sealant whatsoever. I discovered this right after I discovered that I could back the nut off the depth sounder 'ducer with my fingers. Fortunately I was playing this game in the yard! They were vintage 1980 and didn't leak - so I guess there's a lot of fudge room in the installation of these things. Sure made me nervous though. All the through-hulls save the one I knew was good came out and were reinstalled!

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 05/20/2004 : 16:11:42

The thru-hulls (not to-hulls) Catalina used when they built my '85 are flush to the exterior, with about a 3" disk that is countersunk into the hull. I suspect that's partly for trailering purposes. (You wouldn't want a mushroom catching on a bunk or bouncing over rollers.) So, there is no mushroom on the outside, but they are not to-hulls.

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smp817
1st Mate

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USA
30 Posts

Response Posted - 05/22/2004 : 09:39:05

Thanks for all the information. As soon as I get the thru-hull I'll get it in. Note: measure inside dimension of part, not outside. Forward thru-hull is 1/2", not 3/4". Also, if you are wanting a part from West Marine sent overnight, be sure and order before their 11:00 am cut-off time.
Steve Perry
#5883 "Love & Luck"

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