Thru Hull Modification

Apr 19, 2019
30
Catalina 30 Proud Mary Forked River
I have purchased new thru hulls and seacocks for my Catalina 30.
The new thru Hulls are smaller (both in diameter and width to the originals).
Thought I had it worked out with distributor but miscommunication resulted in this situation.
Diameter difference old 2-3/8" new 1-1/2"
Width difference old 3/8" new 1/4"

Any suggestions on best way to fill in area around and secure new thru hull.
Thru 1.jpeg Thru 2.jpeg
 
Sep 30, 2008
1,426
Catalina 310 Quincy, MA
I don't know, Jac, that's a big difference in size and water flow. You would have to fill in the existing holes and re drill new holes. I think I would put those new valves on E-bay and get the correct sizes.
 
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Apr 19, 2019
30
Catalina 30 Proud Mary Forked River
Yea, I thought it would be a simple replacement.
I wanted to use composite seacock with a flange but it seems like you can't buy them with the original size thru hull.
 
Nov 7, 2011
2,462
Catalina 30 Mk II Barnegat, NJ
Welcome to the forum @Jac123 !
This is a good place to ask your question. If there's a solution, somebody here will have it.
 
Jun 10, 2017
167
Catalina 1980 Catalina 30 Mk II South Pasadena / Tampa Bay
JA,
I agree with Tom. I don't know who you got these from so, give Catalina a call in Largo Florida
@ 727.544.6681

They should have what you need. Also please do not use gate valves. Look into Delrin ball valves. They will not freeze or have stem leakage & are NOT subject to electrolysis.
 
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Feb 8, 2014
1,084
Columbia 36 Muskegon
Making the holes bigger is of course easy, but smaller not so much. Essentially you'll have to close up the new holes as if you were eliminating an unused through hull. Should be lots of threads here and other forums on how to do that. It's a big job. Sounds like a good opportunity to reevaluate the placement and number of holes you have. Less is always better.
 
Nov 7, 2011
2,462
Catalina 30 Mk II Barnegat, NJ
Jun 21, 2004
1,226
Beneteau 343 Slidell, LA
Try to return them and get correct sizes. Might lose a few days to get new ones, but save lots of grief trying to retrofit.
 
Jun 4, 2004
95
Oday 34 Niantic
Hmmm... what am I missing here? Looks like same size thru hull to me. It is an entirely different STYLE with a different size and design outer flange. Diameter of the threaded portion and inside diameter (water flow) look the same to me. Either glass over the recess for the outer flange and refit or return and ask for the same STYLE. A bigger size will result in a bigger hole thru the hull, different tailpiece being needed, changing hose, etc. etc.
 
Oct 22, 2014
9,984
CAL 35 Cruiser Portland OR, moored EVERETT WA
And you may find that the space of the interior compartment may not work for the new sized backing plate and valve. Check both sides of the hole.
 
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Apr 19, 2019
30
Catalina 30 Proud Mary Forked River
Your correct- Same size thru hull but as I was later informed does not come with the original size skin. Hard to believe that no after market composite seacock with flange or collar matched with the original size skin exist.
It seems like there must of been hundreds of boats built with flush skins and just valves on thru hulls produced.
Thanks for your feedback.
 
Sep 30, 2008
1,426
Catalina 310 Quincy, MA
Your correct- Same size thru hull but as I was later informed does not come with the original size skin. Hard to believe that no after market composite seacock with flange or collar matched with the original size skin exist.
It seems like there must of been hundreds of boats built with flush skins and just valves on thru hulls produced.
Thanks for your feedback.
Sorry, Jac, I'm confused. I thought in your OP, you said the new thru hulls were smaller. If they are in fact the same size, then what I suggested does not apply.
 
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Apr 19, 2019
30
Catalina 30 Proud Mary Forked River
Sorry, Jac, I'm confused. I thought in your OP, you said the new thru hulls were smaller. If they are in fact the same size, then what I suggested does not apply.
Yes, I didn't state it clearly. It's the skins outside dimensions that are smaller - the opening is the same. So far in composite I can find a skin that matches the original but not a seacock (only a valve) that threads to it.
The Bronze Groco skin is close - about 1/2" smaller in diameter. If I use 5200 can I bead a 1/4" around the skin to "fair" it into the hull ?
 
Sep 30, 2008
1,426
Catalina 310 Quincy, MA
Yes, I didn't state it clearly. It's the skins outside dimensions that are smaller - the opening is the same. So far in composite I can find a skin that matches the original but not a seacock (only a valve) that threads to it.
The Bronze Groco skin is close - about 1/2" smaller in diameter. If I use 5200 can I bead a 1/4" around the skin to "fair" it into the hull ?
I wouldn't use the 5200 on the thru hull, it will never come off again. A better sealant for the thru hull itself might be 4200. For the outside flange, maybe build up the area of the hull with an epoxy fairing material and then shape it to get close to the dimensions of the flange.
 
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Apr 19, 2019
30
Catalina 30 Proud Mary Forked River
I think I'm going to give Tom J's method a shot. I was thinking of buying a sacrificial thru hull and setting it in place. Covering the threads with tape and then the tape with some sort of release agent. Applying epoxy around it and when cured removing the sacrificial and installing the new thru hull with 4200. Any thoughts on hull prep, release agent, epoxy, how to keep epoxy in place would be appreciated
 
Nov 7, 2011
2,462
Catalina 30 Mk II Barnegat, NJ
@Jac123 ,
I know I said I was going to use 5200 for my thru hull install but I changed my mine and went with Siki Flex 291. It's what Maine Sail used in his www.marinehowto.com article on installing thru hulls. Not quite as aggressive as 5200.

I question the thread compatibility of the Groco bronze thru hulls. According to this excerpt from the Forespar Marelon catalog they use a different thread on the Series 93 thru hull/seacock. Here is a screen shot from their catalog about the threads:

Forespar Marelon Threads.jpg

Their "Series 93 Threaded Valves" use the marine standard straight thread, one of the reasons I chose to use that valve. The thread type matches their CF250 thru hull, which matches the ones I took out of the boat.

I installed my new thru hulls and valves on Sunday.
Series 93 Threaded Valves.jpeg

BTW, the shape of the hull at the intake thru hull opening may make it tough to fit the flanged thru hull flat to the hull. My 3" backing plate had to be trimmed due to the curve of the hull.


Attached is the Marelon catalog.

Maybe @FastOlson will see this thread and compare what you have to what Marelon valve he used.
 

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Apr 19, 2019
30
Catalina 30 Proud Mary Forked River
@FastOlson
Did the OD of the flange lip on your thru hull look the same size compared to the old white one in the photos @Jac123 posted?
Yes, thats what I'm thinking about filling in with the epoxy to match the skin of the 93 thru hull. Have not worked with epoxy and am wondering
if it will "slump" before curing? Also if it will adhere to the hull as well as 5200 would?
 
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