How thick is hull for thru hull in bilge floor

[catspajaumas]

1973 CHB Sedan trawler.
Need to know thickness of floor in the bilge.
Need to replace generator thru hull seacock mushroom.
Any ideas?
Thanks

 

[Comodave]

1973 CHB Sedan trawler.
Need to know thickness of floor in the bilge.
Need to replace generator thru hull seacock mushroom.
Any ideas?
Thanks

It would actually be the hull thickness that you need to know. If it isn’t a cored hull, most likely not, then probably about 3/8” to 1/2” thick.

 

[psneeld]

Could be thicker.... up to over an inch depending on where in the hull it is located.

But any decent sized through hull will fit.

 

[Comodave]

Yes, usually they are too long and you may have to cut them down a bit in a proper seacock installation.

 

[psneeld]

A nice thick backing block and cutting down may be avoided.......

 

[Pete Meisinger]

Near the keel, which is where you want to put the hole, it is around half inch thick.

pete

 

[psneeld]

On my Albin 40 it was much thicker...but as I said...doesn't really matter as the through hulls will normally accommodate and just adjust the backing plate thickness as desired.

 

[mvweebles]

Slightly off topic, but this Marine-How-To article on installation was super helpful to me. The Groco adapter plate is pretty cool.

https://marinehowto.com/installing-a-seacock-in-a-new-location/

Peter

 

[CharlieO.]

You don't want to go through the bilge floor, that will be a thin layer of fiberglass over the concrete filled keel, you will want to go outboard of your stringers thru the hull. Assuming you have a single engine with the keel.

 

[psneeld]

Sounds like he is replacing so the location is already determined.

Agree the Groco flange and ball valve setup is nice... I had to replace a badly gooped up waste discharge ball valve. Could easily do it in the water without a haul out as it is just unscrew the ball valve and quickly screw on the new one. That savings alone paid for the upgraded system on all my underwater through hulls when I purchased the boat.

https://www.groco.net/products/valves-seacocks/flanged-valves/ibvf-flange-adaptor

 

[CharlieO.]

Sounds like he is replacing so the location is already determined.

Agree the Groco flange and ball valve setup is nice... I had to replace a badly gooped up waste discharge ball valve. Could easily do it in the water without a haul out as it is just unscrew the ball valve and quickly screw on the new one. That savings alone paid for the upgraded system on all my underwater through hulls when I purchased the boat.

I think they need to replace the 'mushroom' also, not just the valve.

 

[psneeld]

I think they need to replace the 'mushroom' also, not just the valve.

I was just suggesting if you need to replace the mushroom, switch to the new system so the next time, if ever, it is easier to deal with.

Unknown reason for replacing the mushroom, if electrolysis or other electrical damage, probably a good idea to replace the seacock on top of it.

If it was just a ball valve on the mushroom, good to go to a true seacock anyhow.

Plus, om my Albin, the main engine and A/C through hulls were between the main stringers so the "false floor" varies. But as the OP posted, he is replacing so the location is probably OK (unless it was just put in where the false floor is and that's the problem )

 

[EngNate]

It's practical to measure and cut, not predict, the exact length needed.

 

[ramkay]

My 1978 GB32 is 1cm (3/8th of an inch) thick. That was the on-going trend in the 70's.

 

[angus99]

Agree with Scott (and Rod) on the Groco flanged adapters, composite backing plates and ball valves. I put 13 of them in my boat and they make the job easier while making for a much more secure install than the ones they replaced.

I had a hole cut in the hull last week for a new transducer and was pleased to find it was quite thick three feet from the centerline and getting thicker inboard toward the keel.