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Author Topic: Replacing Thru Hulls  (Read 185 times)

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sloopdog

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Replacing Thru Hulls
« on: April 23, 2021, 06:04:00 PM »

Hi All,

I'm planning to replace all my thru hulls on my 1988 in June.  I have one that seems to be slightly leaking and a 1.5 inch bronze that is seized so I figure might as well get to the others and be done with them for another 3 decades.  I'm planning on installing tru designs as I would really like to stick to a non metal material.  The issue I'm having is confirming what size my thru hulls are.  I do know they are flush and not mushroom.  Can anyone confirm if my below info is correct before I start ordering?

Engine intake (under head sink) 3/4"
Toilet Intake (under head sink) 3/4"
Sink/Shower drain (under head sink) 3/4"
Prior direct waste discharge (Hanging closet next to nav station) 1 1/2"
Sink Drain (Under Galley sink) 3/4"
Macerator discharge (under port settee) 3/4"

Thank you. 
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Noah

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Re: Replacing Thru Hulls
« Reply #1 on: April 23, 2021, 06:25:15 PM »

Sounds correct to me. However, not sure why you have or need two thru-hulls for head discharge. If you have a macerator pump installed why?  My boat is set up with 3/4 thru-hull after macerator. When it is open it discharges into the sea, when thru-hull is closed, you suck out waste through deck fitting waste discharge. The terms: “thru-hulls” (aka skin fittings”) are different than the “valves” (aka seacocks). The thru-hulls come in flush or mushroom-style and then you match the valves to them. I would look at Forespar or Truedesign for non-metallic ones. I replaced my valves with Forespar Series 93.
« Last Edit: April 23, 2021, 06:50:07 PM by Noah »
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1990 hull #1014, San Diego, CA,  Fin Keel,
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sloopdog

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Re: Replacing Thru Hulls
« Reply #2 on: April 23, 2021, 08:26:00 PM »

Yes I'm sold on the trudesign at this point with the load bearing collars.  I'm going to go both valve and thru hull from them. I believe the 1.5 thru hull was initially used for direct discharge. I was going to either delete or just put a new thru hull in. New thru hull route seems easier.

Thanks for the feedback on sizing. How did replacing go for you? Any challenges other than the expected?
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Noah

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Re: Replacing Thru Hulls
« Reply #3 on: April 23, 2021, 09:02:14 PM »

The Forespar Series 93 Marelon valves/seacocks/thru-hull system is highly rated and designed to protect against breaking off— a somewhat similar concept to the Truedesign collar-concept, but not as bulky I believe. However; my valves are a bit stiff to turn for my liking. I wish the handles were a bit longer for more leverage. Mainesail has a test/write-up about the Series 93 on his Compass Marine How to Website.

I also unbeknownst at the time; I did not do enough homework prior the replacing old stuff. I  could not find Marelon thru-hulls (skin fittings) that matched the existing flush bevel taper of the holes in my boat: so I used Buck Algonquin bronze thru-hulls matched to the Marelon Seris 93 valves which worked fine. Since then Ken Kloeber has pointed out that Forespar does make a thru- hull with the correct flush taper. To match our factory bevel, but my “ship had already sailed” so to speak!  So I have bronze flush thru-hulls with Series 93 Marelon Forespar valves attached. I also made 1/4 in:  G10 backing plates for each valve: there is lots of info on our website if you search.
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1990 hull #1014, San Diego, CA,  Fin Keel,
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sloopdog

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Re: Replacing Thru Hulls
« Reply #4 on: April 24, 2021, 09:59:12 AM »

Good to know on the taper. I'll have to search around for ken's post to try and get the dimensions of the taper.  I'm hoping to use the flush trudesign thru hills but if they don't have the correct taper it would make sense to just purchase the forespar units and pair them to the trudesign valves.

I have a bunch of g10 I was planning on using to add backing plates. Did you just epoxy to the hull or actually glass them in?
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Noah

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Re: Replacing Thru Hulls
« Reply #5 on: April 24, 2021, 10:27:28 AM »

I just “buttered” them to hull with thickened epoxy.
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1990 hull #1014, San Diego, CA,  Fin Keel,
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Noah

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Re: Replacing Thru Hulls
« Reply #6 on: April 24, 2021, 10:41:05 AM »

This is what Ken K. Sent me in 2018 after I did mine with bronze Buck Algonquin thru-hulls and Series 93 valves:

“CF250, 53 deg bevel thru hulls fit the Catalina holes perfectly. The 3/4” CF250 dimensions out to a little over 2.4” (per Forespar literature, if one believes literature...” I would check it put for accuracy and fit.
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1990 hull #1014, San Diego, CA,  Fin Keel,
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sloopdog

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Re: Replacing Thru Hulls
« Reply #7 on: April 25, 2021, 03:18:39 PM »

Thanks for the pictures.  Looks exactly what I'm planning with the G10. 

I looked up the forespar thru hulls that are reported to fit our hulls and I've attached the diagram below along with the trudesign diagram.  They are definitely not the same so I think I'm going Forespar marelon thru hull with trudesign valves.  Hopefully the attached will help someone to be able to refer to in the future.  As you can see on the trudesign is stepped instead of flared out.  Truedesign also is significantly less flared as tit ends up at about 1.65 inches round as opposed to the Forespar which goes out to 2.43 inches.

Thanks for the heads up. Otherwise I would have been buying the trudesign thru hulls and probably end up with the same issue you had. 
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Noah

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Re: Replacing Thru Hulls
« Reply #8 on: April 25, 2021, 06:02:18 PM »

As a last resort you could glass in/fill-in old bevels and re-bevel holes to whatever flush mount fitting that comes with Truedesign valves set. Depends on how much work you want to do...
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1990 hull #1014, San Diego, CA,  Fin Keel,
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