Thru Hull

[CaptainHatty]

I'm not sure this is the right Thread Topic, if not I appologize.

My question is in regards to the 'proper' or 'approved' method of installing a thru hull. I've done a bunch of research and was planning on using a Tri-Flange Adapter. I was recently at a local marine store and someone there told me that this method was not Coast Guard Approved? He said the Seacock
method was the only approved method for a thru hull.

It seems like the Flange Adapter is a much more versatile installation with benefits such as allowing you to change the valve without replacing/removing the entire thru hull.

I've contacted a Vessel Saftey Check inspector associated with the US Coast Guard Auxiliary and he said it was a question outside of an inspectors resposibilities. The gentlemen at the Marine store said if we got boarded by the USCG the Flange Adapters would be an immediate red flag?

Can I use the Flange Adapters, or not? Anyone have any experience with them?

Thanks,

[hanleyclifford]

If anyone tells you something is not "Coast Guard approved" ask them to cite a chapter and paragraph from CFRs or provide a link. The flange adapter is a splendid idea and solves a serious issue regarding the mixing of straight and tapered NPT.

[Bold Rascal]

here's a helpful link

http://www.pbase.com/mainecruising/replacing_thruhulls

Hope it helps you as well

[tenders]

"Mainesail"'s richly photographed monograph is the best coverage of this general topic that I've seen anywhere:

http://www.pbase.com/mainecruising/replacing_thruhulls

Actually all of his stuff is top-notch.

http://www.pbase.com/mainecruising/boat_projects

[dvd]

Yeah, if you do it like that it ain't goin anywhere. Wish mine were all like that.

dvd

[CaptainHatty]

Those Compass Marine links are where I've been getting most of my information and is exactly what I was planning on doing (probably the Alternate method). Sadly, the flange and the seacock don't have the same bolt pattern (I checked yesterday). Since they're different, I really don't want to go to all the trouble of making and installing the backing plates only to have the tri-flange be a problem with inspections/surveys..
Any suggestions on where to get a definitive approval on the tri-flange?

[Bold Rascal]

I can't guarantee it but,,,

You might try contacting either of the provided links. Possibly Niel Dutton or another member may be of help.

Do you know any local marine surveyors?

[Mo]

I think Hanley and Neil are excellent sources of information as well. When I did mine I put a standard thru-hulls (2007). I had not heard of these flange adaptors at the time. Actually, this is the first I've heard of them.

[tenders]

Those flange adapters, simple as they are, are new in the last five years or so and are I think patented by Groco.

Any marine surveyor who prefers the wrong way (mismatched threads and wooden backing blocks) over those robust slabs of bronze should be escorted out of the boatyard.

I would personally rather have sealed through-bolts in my through-hulls rather than the threaded-in-G10 alternate method of Mainesail's. The alternate method seems like a lot more work too.

[ndutton]

I didn't do too much digging but what I did find was at least a portion of the ABYC requirements.

As for installation specifics, I found none. What was specified was that the thru-hull installation shall be capable of withstanding a static 500# side load on the assembly tailpiece (where the hose attaches). That pretty much eliminates everything except a through bolted seacock I think. I'm not saying a thru-hull, wood doughnut and ball valve won't comply but it too has to withstand the 500# load to meet the standard.

Mention was made also about the mismatch of straight thru-hull threads and tapered valve threads. The problem cited was only three or four threads engage before binding and it is assumed the fit will never meet the 500# standard.

Regarding bolted seacocks, those with cored hulls need to take special care. You cannot effectively bolt through the core.

[KeysCatalina]

Thanks for the links.
I want to replace my thru hulls this summer when I have the bottom job done.
I like the idea of the tri-flange for extra strength. My big question is marelon better than bronze? I think my existing are original and bronze but have turned green. Also they have round knob valves like a water spigot so im afraid to even try and turn them in case they break off.
Will marelon last 30 years? Im looking for the longest lasting material possible so I only have to do this job once.

[msauntry]

I hate the marelon valves because I've had the handle snap off in my hand. Think 30 years from now (or next year) when the valve is a little sticky that the plastic handle is going to hold up? These are not nearly robust enough to handle the abuse that boat owners throw at them. Nobody greases the vavles every year, as well intentioned as we may be. Also, no matter how green your bronze gets, you can always clean that off with a wire brush or a little weak acid.

I agree, replace the gate valves that you have, but replace them with bronze if you want them to last.

[smosher]

I have 2 marelon thruhulls and valves with no issues. I find them very easy operate vs my bronze ones, which I do grease every year.

When you replace the thruhull make sure you use the correct valve threads, IF I remember correctly, most valves are npt and the thruhull is a straight

Steve

[ILikeRust]

I followed the Compass Marine article and I can't imagine how I would ever have a problem with it or how any subsequent buyer or marine surveyor would either. The surveyor I hired didn't say word one about the extremely sketchy through-hull that was in there when I bought the boat. I'm surprised it kept the boat afloat, actually.

Neil can tell you all about marine surveyors...

Just one man's opinion, but I would use the three-bolt flange adapter without hesitation. In fact - I did!!

[sastanley]

Keys, like Micah, I went to Marelon & have been very satisfied.

I have epoxy coated wood or PVC (plastic) backing plate (depending on the thickness I needed) in my Catalina 30. I 5200'ed the thru-hull to the hull & backing plate (used the nut from the thru-hull fitting to clamp) and then removed the nut and screwed on the marelon seacock. I cheated just a little bit and instead of thru-bolting the seacock flange, I used 1" sheet metal screws and screwed the seacocks to the wood/PVC that was previously bedded with 5200.

I think the keel is more likely to fall off than for these fittings to fail.

YMMV of course, but I have not had any problems with mine.