Capping a thru-hull

Jim Lucas · June 05, 2020, 10:09:42 AM

I've been stuck coming up with the best solution for capping off an old (Espar heater, I think..) exhaust thru-hull. It's about 2.5" and well above the water line. It looks like it was just cut off near the hull and stuffed with a cork bung. It's one of the last items that the surveyor pointed out that needs to be "properly capped".
Any suggestions on best method of capping this?

KWKloeber · June 05, 2020, 11:10:04 AM

Jim

I'm not at all familiar with that particular thru hull and the pic doesn't reveal a lot.
Is the outside body smooth/flush/round- I'm thinking a Fernco rubber cap over the top? Replacing the usual s/s slotted band clamp with an embossed clamp (ABA or WAWB brand).

What is the material? Would epoxy bond to it - I'm thinking fill it?

Ken

Noah · June 05, 2020, 11:59:50 AM

I am sure there are some creative ways to jerry rig it, but in IMO if you can't find a matching screw-on cap, or no threads remain on thru-hull to affix a cap to, then;
1. replace thru-hull with a new similar size thru-hull and seacock with valve/capped-off
Or
2. Remove old thru-hull and fiberglass the hole "properly" after grinding a 12:1 bevel inside and out.

Jon W · June 05, 2020, 12:23:23 PM

Where on the boat is it located? Do you have a picture you can attach?

Jim Lucas · June 05, 2020, 03:04:18 PM

I'll have to get more photos when I get back down to the boat but this is located reasonably high up on the Port quarter. It appears there's no threads left that could be used for screwing a cap onto and a proper fiberglass repair would be ideal. Perhaps a replacement thru-hull that can be properly capped off would be the most cost effective and better than some additional jury-rigged material and hose clamp.

scgunner · June 06, 2020, 07:00:50 AM

Jim,

If it's a through hull that's not going to be used and it's above the water line then basically you've just got a hole in the hull that needs to be patched, it's just a fiberglass repair job followed with some painting and blending.

Roc · June 08, 2020, 12:13:49 PM

Well, the best thing to do with your holding tank vent is to provide two vents for cross ventilation. This provides oxygen in the tank to promote aerobic bacteria (as opposed to anaerobic, which is what causes the smell). A high thru hull for the second vent is what is advised. I did that on my tank. If your tank is on the same side of this thru hull, you might want to re-purpose the hole.

Jim Lucas · June 08, 2020, 02:37:23 PM

I was just about to respond; scgunner, I think you're quite correct and glassing this over is truly the right way to do it.

But, Roc, cross venting the holding tank is a great idea! This is on the same side of the boat and should be able to run a second vent hose. A cheap fix and re-purposing a problem into a solution.
I work hard on keeping the holding tank well maintained and the added vent would be ideal!

Thanks guys!

Jon W · June 08, 2020, 02:48:21 PM

If you use it as a holding tank vent, will it get submerged when heeling underway?

Jim Lucas · June 08, 2020, 03:23:07 PM

I don't think so. It's located a few inches below the rub rail and far enough astern so that shouldn't be a concern.

Jon W · June 08, 2020, 04:27:45 PM

I'd make sure. You don't want to fill your holding tank from water ingress.

Dave Spencer · June 08, 2020, 04:35:26 PM

Jim,
If you do a holding tank cross flow, there's lots of discussion about that here. I did it several years ago and documented it in this post - Reply 17.

https://c34.org/bbs/index.php/topic,6861.msg45889.html#msg45889

Another option would be to relocate the bilge pump discharge to higher up on the hull. I'm not too happy about my discharge just inches above the waterline (and usually submerged under power) under the swim platform on my Mk 1.5. The flimsy bilge hose is fine for bilge discharge but I get nervous when I see it underwater. A "to do" project is to replace the bilge discharge flange with bronze or stainless and replace the hose with something a bit more robust.

Roc · June 09, 2020, 10:13:34 AM

I have a second holding tank vent placed right below the rub rail, port side. Exits the hull about were the closet is in the v-berth. It's well above any heeling angle. It's placed forward so as the boat moves, it will push any air going in into the tank. This was advised by Peggie Hall, expert in waste management.

mdidomenico · June 09, 2020, 10:28:27 AM

i think i may have drilled my hole to far aft based on what you all are saying. i drilled my new tank vent hole just below the rub rail, but basically where the old stanchion vent was. i may have to have the fiberglass guy fill it when he fixes my bow roller area. i figured there'd by some spray or the occasionally wash along the rub rail when heeled over, but i didn't think i'd be heeled over that far for that long that i'd siphon the sea into the tank. mistake number 10k, argh

Jim Lucas · June 09, 2020, 11:18:53 AM

I like the idea of having the vent forward for air flow but wonder just how much air would be moving through verses the possibility of forced water.
The existing exhaust vent at the rear port quarter and high up near the rub rail seems to be a safer bet as it would be even harder to create conditions of burying that area. I'm thinking if I leave the existing station vent and add the rear vent, I may get some flow through venting.