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grampianvoyager 05-08-2014 08:12 PM

Thru Hull Fitting
I just purchased a Grampian 26 and have a question on the thru hull fitting.

I can't post a pic until I have 10 posts

Is this right for the original thru hull or is the flange broken off? It is glassed over on the inside. If the picture doesn't show I started a blog of my progress with the post at the top (for now).

grampianvoyager 05-08-2014 08:14 PM

Re: Thru Hull Fitting
sorry that's

Faster 05-08-2014 10:18 PM

Re: Thru Hull Fitting
I see no evidence of any kind of 'through hull fitting'.. looks like a glassed in stub (that may originally have been a f/g tube to the cockpit sole if it's a cockpit drain) Looks like someone somehow fit that gate valve into the f/g stub.

That's the wrong kind of valve, by the way.. a 90 degree ball valve is a better style for that job. Cutting out that stub and installing a real thruhull valve would be the 'proper' fix.

Have a look here:

Replacing Thru-Hulls and Seacocks Photo Gallery by Compass Marine How To at

grampianvoyager 05-09-2014 08:25 AM

Re: Thru Hull Fitting
Thanks for the info Ron. I think I do have a glassed in stub. It is for the sink drain. I am only in fresh water (Great Lakes) so corrosion shouldn't be a problem now. The thru hull recommended on your post are the three bolt mount type. This makes 4 holes instead of one. Is using the fitting with just the compression lock nut not recommended?

Faster 05-09-2014 10:37 AM

Re: Thru Hull Fitting

Originally Posted by grampianvoyager (Post 1822618)
.... Is using the fitting with just the compression lock nut not recommended?

There are many boats with throughulls such as you describe, and that's another viable method, somewhat less costly, perhaps, and simpler too - but the bigger issue there is that often those through hull fittings are not NPT/tapered threads so when you attempt to mount a threaded NPT valve on them you're lucky to get a full turn never mind several before the threads bind up.

The 'holes' used to mount the "Cadillac" fittings are not 'vulnerable' holes like the through hull itself and easy to seal when properly done.

If you peruse the rest of Maine Sail's site IIRC there's a section on the thread mismatches there too..

grampianvoyager 05-09-2014 05:41 PM

Re: Thru Hull Fitting
Thanks Ron. I see your point. I will at a minimum replace the valve this year. I posted my question and your answer on my blog. It is a good safety point to look for. I hope you don't mind.

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