Friday, January 30, 2015

Marelon Seacocks

We had a near catastrophic situation when after a nice day of sailing, I went to close the head seawater intake thruhull and the handle popped off in my hand.  Sea-water immediately started flowing in.

The handles are secured to the seacock ball by a 3/8" screw.  There's also a o-ring around the shaft of the handle and the screw to seal the seacock.  After the handle pulled out of the valve, I tried to put the handle back into the valve, to stem the flow of water.  I discovered that the o-ring became dislodged and pressed into the body.  This prevented the handle from seating into the valve.  Meanwhile, water keeps pouring in to the boat.

Using a small screwdrive, I removed the o-ring (all while water is pouring in), reassembled the handle and was able to properly insert and secure.  This is a terrible design, though I guess it lasted 14 years before the threads wore.

The solution turned out to be very easy.  I obtained 2 replacement seackcock valves from Forespar.

Notice the valve is made in 4 sections, held together by 4 large bolts from the top.  There's the threaded thuhull (white, not shown), that screws into the 3 1/2" diameter base, ball valve assembly (middle, where handle is attached), and top assembly.

Forespar's new design uses an embedded nut and bolt to hold the handle to the valve (I checked).  This should be more secure than the 3/8" screw.  Otherwise, the valves are identical.  What that means is you can replace the middle section, and don't have to haul the boat to replace the thruhull!!!!

Notice the white plug on the handle (above)?  It turns out this is the proper size to fit the thruhull from the outside of the boat.  I guess their idea is if the handle breaks off and the boat is sinking, you can jump in the water and plug the thruhull with this little plug.  Right..... I had my diver plug these, the next time he cleaned the bottom.

With the thruhulls plugged, I cautiously took apart the seacock,

Pay attention to the squarish gaskets between each of the marelon pieces.  Per the instructions, I applied a bit of marine grease to these and reassembled.

One final note, the seacock clearly states to not disassemble the valve,but Forespar's technical support encouraged me to do exactly this!  It is great when the design is improved and the parts are interchangeable.  It would have been just my luck if the assembly was 1/8" different is size or the screws were moved.

I replaced both the smaller sea water intake seacocks.  I'm relieved that these are operational without the fear of the handle coming off and flooding the boat.  The fix was very easy.  I'm thinking about swapping out the ball-valve on the remaining 3 seacocks in the boat.

Don McLennan
Intuition - 3500 - #115

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