Marty Chin, who manages Bay Marine Diesels in
San Francisco, sent us the following letter, which
we feel is worth sharing. The Groco seacocks he
describes are a different model than we have on
Taleisin. The ones we use on Taleisin were made
by Groco, but instead of having a stainless ball
and Teflon seating, they have expandable rubber
cones. We added grease cups which we tighten down
twice a year to keep the cone and bronze seat
lubricated. After 23 years they are still in fine
Thank you to Marty for permission to share
this info -
We recently hauled our BCC Shamrock and took a
look at the Spartan seacocks in our boat, current
production Bristol Channel Cutters use Groco.
Our original plan was to replace them with Groco,
which seem to be some of the better through bolted
seacocks on the market.
The Groco seacocks with the stainless steel ball
and teflon seat seems to give a good clean seal,
the teflon act as a wiper, cleaning the ball if
the valves are cycled open/close often. We did
note as with most teflon/ss or chrome plated ball
type valve, if left closed for prolonged periods
of time, the ball became pitted or encrusted with
mineral deposits, when the valve was cycled the
deposits/pitting tended to score the teflon seat
causing the seacock to leak internally around
the ball; if the hose failed, closing the valve
slowed but failed to stop the leak.
Our severely neglected Spartan seacocks suffered
the same fate of leakage around the bronze tapered
plug. We lapped 4 of the 1-1/2 and restored them
to new condition; the 3/4" seacocks were
not salvageable due to long-term neglect. We later
removed the mushroom thru-hull fittings and found
they had been cut to short, only 2-4 treads engagement,
the majority of the threads were exposed to the
sea and subsequently were lost to electrolysis.
It was a tough choice, but we decided to replace
all the seacocks with Spartan seacocks to keep
it simple, allowing us to disassemble, clean,
lubricate or lap if necessary at each haulout.
This time around we measured the hull thickness,
backing block thickness and total thread depth
of the seacock and cut the mushroom thru-hull
fittings 1/16" short to get maximum thread
grip inside the seacocks, in addition to the 5/16"
bronze thru-bolts. We also added a little Sikaflex
291 to the threads of the thru-hull to prevent
water from migrating along the threads, same sealant
we used to bed the thru-hull fittings and seacocks.
We were impressed with the massive construction
of the Spartan seacocks, the handles are pinned
with a 1/4-20 SS allen screws threaded through
the handle and pass through a large rectangular
lug on the plug, we still have 6 used handles
in new condition, I swear the handles last forever.
We purchased Groco thru-hull fittings, they are
CNC machines, no crude castings, threads are cleanly
cut not rolled and the price from local distributor
was the lowest on the market. The Spartan website: