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With three or four adults on-board cockpit/sink drain through-hull stays permanently submerged below water line without any possibility to stop flooding boat if cockpit/sink drain hose fails.

A few seasons ago I found a few gallons of water under rear berth after winter storage. I found ruptured hose between through-hull and outboard well drain. It froze over the winter and ruptured. It could lead to a disaster with through-hull submerged.

I don’t use sink at all and was thinking that it would be nice to get rid of that through-hull. I was thinking of drilling 3/8” hole next to outboard mount just above outboard well floor level and plugging existing outboard well drain. Then I could disconnect sink hose and plug cockpit/sink drain through-hull.

Do you see any potential problems or something I am overlooking doing that?

Thanks!!!

The motorwell and galley drains are for convenience and could be disconnected & plugged to eliminate the potential issues you describe. Just bail or sponge out the water in the motorwell before it gets murky.

I found a couple of threads in the archives on the 26M motorwell from 2007 and 2009 but can't make a link to them like I used to.

I have the same concerns. Heavy aft puts it under. And that thru hull is cheap without a seacock. So a failure could be catastrophic.

Got no solutions other than yours. I do worry about it as the hoses don't seem very substantial either.

--Russ

RussMT wrote:I have the same concerns. Heavy aft puts it under. And that thru hull is cheap without a seacock. So a failure could be catastrophic.

Got no solutions other than yours. I do worry about it as the hoses don't seem very substantial either.

--Russ

I was thinking of installing a seacock on outside and remember to close it every time I check water ballast before going out. I thought of using Groco BB-1 backing block epoxied around existing thru-hull with Groco BV-750 seacock. But existing thru-hull is too close to ballast valve.

But since I don’t use sink at all I will permanently plug everything and drill 3/8 hole through the motor well wall as low as possible to allow motor well drain outside.

Thanks for your feed back!

Maybe just stick a cork in it ?? Ron. Dauntless. Actually I worry about the same thing as well as the motor well drain gets plugged too easy...

hmm. How about this? Have safety and confort?

My idea: Put new thru-hull 30cm above waterline. Install the pipes to the new thru-hull, but go first to an automatic bilgepump that just works when water arrives. Maybe it can be bought ready to go if you buy the thing that you use when you install a shower.

then the bilge is drayned all time, and the kitchen you can use the same manner than before. And the thru-hull is save...

kurz wrote:hmm. How about this? Have safety and confort?

My idea: Put new thru-hull 30cm above waterline. Install the pipes to the new thru-hull, but go first to an automatic bilgepump that just works when water arrives. Maybe it can be bought ready to go if you buy the thing that you use when you install a shower.

then the bilge is drayned all time, and the kitchen you can use the same manner than before. And the thru-hull is save...

If it was just sink drain then thru-hull could probably be relocated a few inches higher and the sink would still drain. But motor well wouldn't.

May be the way to go is to install new thru-hull 4" higher with just sink hose connected to it, then permanently plug motor well drain and existing thru-hull. Then drill motor well drain hole through transom next to outboard mount.

I don't know the particulars of the M type thru-hulls, but why not just install a proper thru-hull with ballcock? Most boats over dinghy size have thru-hulls below the water line, and there's no problem with them as long as they're good quality, and inspected regularly, with the shutoff cycled every now and again.

And the sink certainly could be drained through a separate thru-hull, above the water line (well above, in fact), independent of the motor well drain. Like right out the side in the vicinity of the sink.

I'm guessing the only reason they were combined was because it was cheaper to run a length of hose, which they had to do anyway with the moving galley, than it was to add another thru-hull.

Tomfoolery wrote:I don't know the particulars of the M type thru-hulls, but why not just install a proper thru-hull with ballcock? Most boats over dinghy size have thru-hulls below the water line, and there's no problem with them as long as they're good quality, and inspected regularly, with the shutoff cycled every now and again.

There is a chance for seacock installed in this area to freeze in winter. When I cover boat with tarp I still get some rain/snow in motor well. Then depending on weather snow can start melting slowly and freezing again busting seacock.

I am not afraid of underwater thru-hulls done right. I installed one last year for Webasto AC unit. I used Groco seascoop and flanged seacock installed on backing block. It is rock solid.

I think I made up my mind. I will install new thru-hull 4" higher just for sink drain. Drill transom drain for motor well and plug original thru-hull and motor well drain.

I did some research on how to plug underwater thru-hull and couldn't find any blank thru-hulls. I am going to remove thru-hull fitting and use matching size stainless steel bolt with two fender wahsers and lock nut and plenty of sealant to plug hole.

One winter I once did as mrron_tx suggested - used a cork to plug the motorwell drain. It kept the drain from potentially freezing, leaving the puddle in the motorwell to freeze. Unfortunately, the cork broke when I went to remove it and had to disassemble all that plumbing to remove the stuck pieces.

K9Kampers wrote:
Unfortunately, the cork broke when I went to remove it and had to disassemble all that plumbing to remove the stuck pieces.

You didn't have a corkscrew handy? Major mistake

The cork sheared in half as I was pulling it out, then the rest fell apart as I tried to corkscrew it out!

A sailboat is not properly equipped without a corkscrew!

It would be easy to disconnect the drain hose and insert a wooden bung in the hole for the season.

I have a 26x and the stubs of the through hull drains are 3/4" pvc pipe glassed into the hull. I added a short length of clear flex tube approx 5" long secured with double hose clamps. Then used a 3/4" plastic ball valve with a short piece of 3/4" pipe cemented on either end, One end went into the clear flex tube on the through hull pipe again using double hose clamps. The other port of the valve connected to the sink drain via an other clear flex tube with double hose clamps.
The clear tubing makes the state of the drain visible and the ball valve acts as a seacock.
I did the same thing with the sink in the head. I did not use cement to connect the flex hose to through hull pvc pipes, only the double clams, I wanted the whole system to be easily serviced and vibration resistant.
The valves, clamps and tubing came from the local H/W store approx. $30.00.
Hope this helps, works for me.
Bob.

For freeze protection, any loop in the drain hose that could collect water should be eliminated. Shorten the hose as necessary to remove that loop. The constant drain overboard does not build up odors that need to be block as a holding tank might.