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Thread: "W42 Thru Hulls And Sea Cocks"

12,268 posts on 2,444 threads   •   From Mar 07, 2004 - Jan 08, 2012


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W42 Thru Hulls And Sea Cocks

nick cherney (Guest)

bud, or anyone else,
One of the seacocks(original) on our W42 was broken off above the valve and the thru hull was plugged with a wood DC plug just in case. I removed the seacock intending to replace it with a new one, and when I took it off the threaded portion of the thru hull which extended above the wood backing block came right off with it. the whole mess is teribly corroded and will have to be replaced but my question is this. the boat is in the water and I don't want to muck around too much with the thru hull nor do we want to haul out right now. is there anything holding that thru hull in right now other than some silicone? it seems to me there is possibly a big nut which is tightened down against the hull under the backing block, but this would not be the normal instalation and I don't want to pull off the block to find out. likewise I dont want to come back to the boat to find a sad ending if that thru hull is just attached with a bit of sealant. there are the two bolts which potrude into the boat which the seacock was attached to, but they are both corroded and turn freely so they are certainly doing nothing. any info would be great before I do anything rash.

Jeff Holemo

Nick, This one is pretty much a no-brainer...your $150k boat vs a few hundred dollars to pull it out of the water.
I have just removed four of my seven thru hulls and none of them had a nut holding them in. After taking off the seacock...which wasnt easy due to lots of corrosion...the wood block and thru hull came out very easily...a few taps with a hammer was all it took to drive the thru hull out of its hole. I have a W32 with those groco seacocks with the rubber cylinder and two screws holding it to the hull. Be careful if that wooden plug starts to leak and you have to drive it in farther.

Jay Bietz


On my WS32 circa 1976, the thru hull I replaced last winter didn't have a nut under the wood block, as I recall.

I wish I had replaced all the thru hulls as now I have one that needs replacing.

Better to be safe then sorry --



I also had the old Groco seacocks with the two bolts through the hull. I don't recall a nut but would have to check pictures to be certain. I eliminated a few and replaced the rest. Since the bolt holes needed to be filled anyway I glassed them all (I'll leave out the details but could send along with pictures if interested) and redrilled for the new ones. Put new Groco's in that have the three bolt pattern.

Like Jeff said in the previous post, for me it was a no-brainer to just go ahead and replace them.


Jeff Holemo

I am curious about which seacocks you eliminated? I am almost at the point where I either put them all back in or get rid of some...the two draining the cockpit (run the drains to thru hulls above the waterline suggested by Dave King) and one in the head (sink drain which will be run to the shower sump) are the two I am thinking about plugging. And what made you decide to replace them with newer ones? The ones I removed cleaned up nicely (sandblasted em) and the rubber cone still appears to be in good shape.


I eliminated the head sink drain which goes to the shower sump. Next time I haul out I'll do the same with the galley sink drain. I also eliminated the head intake. Use fresh water instead, did this on my last boat also to help keep the odors down. Also plan to replace the depth transducer at next hull out with a depth/speed/temp model (B744VL I think).

Good ideal about the cockpit drains. Will need to think about that.

My boat had been sitting in a shed for 4 or 5 years when I bought it. There were signs that some of the thru hull's had been leaking and the previous owner confirmed that. Decided it was easier to deal with it right away than to mess around with it for a few years and end up replacing them anyway.

nick cherney (Guest)

I have a solution which may interest people in the same situation. Obviously the thru hulls need replacing, but in the bay area that means a thousand dollars or more of yard time, so we will wait until we need to haul out for other reasons. so my solution is to put a screw into the wood plug from inside the boat. this screw will have a large washer and be set thru a wood cross piece which extends beyond the backing block. I will set two wood blocks on either side of the thru hull, which this cross piece will sit against, and tighten the screw to pull the wood plug into the boat. I figure there should be enough force to hold the thru hull in nice and tight for the next year or two. plus if it seems to be loosening I can just crank the screw down again. any ideas out there?

Ed and Elizabeth Pullen

I understand your financial plight - I owned a boat in the bay area and know what it costs. However, have you researched the cost of salvaging your boat if it sinks at the dock, or worse yet, somewhere out in the bay? Additionally, don't forget the value of just about everything inside the boat. Contact BoatUS or USCG and find out just how many boats have gone down because of corroded bronze. Bronze does some funny things - for example, I have seen fittings (esp underwater types) that appear shiny and solid; however, a light tap of the hammer revealed completely oxidized (read that as POWDER) on the INSIDE of the fitting! This is probably stray current destruction - which runs rampant in many areas. If there is any way you can haul (do some yard shopping, including up the delta) and take care of this now, you will be able to sleep a lot better. Even if you have to eat beans and rice for a while...
Ed Pullen
Kibitka W32 0724

Jay Bietz

Hi Nick:
One choice of many boat yards in the bay area is Svendsen's see their rates at


I have heard that they are not the least expensive but as my boat is docked < 100' from the boat lift it's hard to go anywhere else!

Hope this helps.


nick cherney (Guest)

I understand fully that it is more expensive if the boat sinks, which is why I am trying to devise a way to stop the boat from sinking. anyone have any comments on whether they think this approach is a good one or not? I am quite familiar with the yards in the area etc... The thru hull is not going to dissolve, it is simply not secured to the boat so what I need is a way to secure it to the boat, which I think I have devised. anybody have comments on that method or suggestions of other methods? I do appreciate all the advice, its just that I am looking for feedback about how to secure the thru hull to the boat. bud are you out there?

nick cherney (Guest)

interesting possibility, it sets underwater?

Mike McCoy

Have you given any thought to using underwater epoxy putty as a temporary fix to secure the thruhull to the hull from the outside?

It would grind off easily enough when you finally haul it to effect a permanent repair.

Mike McCoy

Yes, it is an epoxy that will set underwater. Used to repair outdrives, etc.. Pretty common stuff. I'm sure I've seen it even at West Marine.

nick cherney (Guest)

a quick update for anyone in the same situation. I have discovered from a local rigger that there is an old tidal grid in Sausalito that can still be used, so I will be able to change the thru hull out with out a trip to the yard, very good news for us as I can rest easy and have enough money to put in some interior lights! thanks all for your help!

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