[Public-list] Installation of a Thru Hull and Seacock

Taylor Echlin taylor at echlinvests.com
Wed Jun 23 07:15:22 PDT 2004

Hi Everyone:

I just had a good experience installing a replacement thru hull and seacock
- and wanted to share with you some information about this.

My Alberg 30 "le papillon" is hull number 612 built in 1977.

Two weeks ago I noticed that the huge flywheel on my diesel had nicked the
cooling water intake hose - not enough to make it leak - but I decided to
replace the hose for safety's sake.

Our Albergs have gate valves attached to the thru hull fittings.  First
thing I did to start my project was to shut off the gate valve.  Then I
loosened the 2 clamps securing the hose to the bronze nipple attached to the
gate valve.

After the water drained from the end of the water hose - I noticed that
water was continuing to dribble from the gate valve.  The rate of flow was
about 1 cup per minute.  The gate valve should have completely shut off the
water from the thru hull.

Even though my cooling water intake is always open - I didn't feel
comfortable keeping that gate valve on my boat - cause it didn't close

So I decided to haul the boat out of the water, and replace both the thru
hull fitting and the gate valve.  We have a travel lift at Port Credit Yacht
Club - so that wasn't a big deal.

I hired a mechanic at Bristol Marine to do the replacement - and he was
really good.  The whole job took 2 hours.

Here's what happened:

 - we hauled out the boat and held it in the travel lift slings (with big
wood blocks under the keel)

 - we removed the cooling water hose from the gate valve

 - we removed the original bronze gate valve from the thru hull fitting

 - we removed the original bronze thru hull fitting.  This wasn't too
difficult.  The thru hull fitting was secured with a locking nut, and lots
of sealant to keep it water tight.  The sealant used by boat builders in the
1960s and 1970s was that grey, putty like material.

 - we removed the plywood backing plate which had been secured with that
same grey, putty like material

 - we then cleaned the hole with acetone, as well as cleaning the fibreglass
inside behind the plywood backing plate

 - I had already purchased a 1/2 inch bronze thru hull fitting with locking
nut, plus a bronze 1/2 inch ball valve seacock, plus a bronze 1/2 inch

 - we then installed the new bronze thru hull fitting and plywood backing
plate and secured both with the bronze locking nut.  We used 3M 4200 fast
cure sealant (I didn't want to use 5200 - because that is a permanent seal)

 - we then secured the bronze ball valve seacock to the bronze thru hull

 - we then secured the bronze nipple to the seacock

 - we then double clampled the 1/2 inch hose

 - we then secured the original Perko bronze strainer cup to the outside of
the hull over the thru hull fitting - and the job was done

 - we launched the boat - and no leaks.  Everything is O.K.


 - the original thru hull fitting and locking nut were both bronze - and
probably didn't need to be replaced

 - the fibreglass hull is 5/8 inch thick at the thru hull fitting

 - the original plywood backing plate was 1/2 inch thick, and dry as a bone
- it probably didn't need to be replaced

 - you could smell the bare fibreglass when we removed the original backing
plate.  Whitby Boatworks had done a really good job on my thru hulls

 - I will likely replace the remaining gate valves when the boat comes out
of the water this fall - and use bronze ball valve seacocks.  Right now I
fell comfortable keeping the original bronze thru hull fittings and original
backing plates - and may not replace them

 - Dan Casey has a good article on "Installing a Seacock" - go to his web

Best wishes.

Taylor Echlin
le papillon  KC 612

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