New Thruhulls and Seacocks

Last year the seacock that supplies Nellie's foredeck washdown and galley hand pump got very hard to move.   This year two Lord Nelsons reported seacock failures.  It was time to take a good look at Nellie's.

Nellie has five underwater seacocks:
1)  1-1/4" main engine raw water
2)  3/4" generator raw water
3)  3/4" supply for both the foredeck washdown and galley hand pump
4)  1-1/4" toilet pumpout 
5)  1-1/4" galley sink drain

  The seacocks were bedded? in a black polysulfide caulk.  The same caulk that OEY used extensively.  The caulk was still pliable, waterproof and, best of all, didn't greatly resist part removal.

I found the OEY original Cheng Wei seacocks to be perfectly serviceable.  There was some mineral buildup but that was removed in a phosphoric acid bath.  Still, the seacocks were 30 years old.  It was time for them to go.

We installed Groco FBV Bronze Full-Flow Tri-Flange Seacocks.

These have the advantage of being through-bolted to the hull.  The thruhulls were also replaced. 

The thruhulls had to be cut to length.   For adequate strength, each thruhull should be screwed into its seacock so that at least four full threads are in contact. 

Since there's about 1-1/4" of thread on the inside of the seacock, the thruhulls were cut 3/4" longer than the hull's thickness.  This easily exceeds the four thread minimum.

The supplied thruhull nut was used to guide the blade.

5/16 x 2" stainless steel, Phillips, flat head, machine screws, lock washers and nuts were used on each seacock.  The screw heads were countersunk into the fiberglass.  The screws were cut so that not a lot of extra length protruded into the tug.

All the parts were bedded in white BoatLife (polysulfide).  It took about 1/2 of a cartridge to do the five thruhulls and seacocks. 

Replacing the seacocks and thruhulls isn't an easy job, the first time anyway, but it's definitely one worth doing.  There are at least two distinct safety benefits of doing this job.  First, through-bolted seacocks are much less likely to have a failure which sinks the boat.  Second, I now well know where all the underwater seacocks are located.