Replacing Thru-Hull Fittings and Seacocks - Part 1

Since Pilgrim's arrival we have extricated five thru-hull fittings and three thru-hull transducers.   I believe the five recessed thru-hull fittings were original to the vessel.  Two of the transducers just forward and starboard of the keel appear to be original.  The third transducer, a newer model, was located mid-ship just starboard of the keel.  

We plan to install a single thru-hull transducer in the forward most existing hole located just  forward and starboard of the keel.  This site is accessed through the panel just forward of the vee berth door.    We have yet to purchase a transducer, and will leave this hole unfilled until we confirm the  diameter of the new unit.

The arrival of our new thru-hull fittings and seacocks has inspired us to focus our energy on filling the old holes and installing the new hardware.

New Forespar Marelon thru-hull fittings (white) and seacocks (black)

The Forespar Marelon fittings and seacocks on C’est la Vie, installed in 1997, served us well and without issue.  The marelon negates the need to worry about grounding to prevent electrolysis.  Thus we are installing identical hardware on Pilgrim. 

In the head…

Exterior view of the original three recessed thru-hulls in the head.

We plan to use one of the existing ¾” holes in the head for the sink drain.  The head sink drain will be the only thru-hull fitting to remain in it’s original position.  Using an original placement requires a recessed thru hull fitting for this site.  All the new thru hull installations will be of the mushroom head variety.  We will install a new 1 ½” thru hull for the offshore black water pump out in the vicinity of the old 1 1/4" hole.   

In the galley…

Below the galley sinks.  We plan to cut away a bit more of the floor to install the new thru-hull directly below the sinks.

We plan to install a new 1 ½” thru-hull and sea cock for the sink drains.  The new thru-hull  will be more in line with the drains and closer to the keel.

In the wet locker opposite the galley sinks…

We plan to install a new ¾” thru-hull, seacock, and filter.  This fitting will serve as a raw water intake for the salt water food pump at the galley sinks and the salt water intake for the head.

Below the quarterberth deck…

The engine raw water thru-hull, seacock, and strainer will occupy the aft (top) section of the newly divided area below the quarterberth deck.

We plan to install a new 1 ½” thru-hull, seacock, and strainer, to serve as the engine raw water intake.  I decided to move the raw water intake to this location to provide easier access to seacock and strainer.  The original raw water intake was under the floor of the portside cockpit locker.

The interior areas around the existing thru-hull holes were ground down during previous projects.

the three existing holes remaining from the original head thru-hull fittings

The exterior required a visit from the 4” angle grinder with a 36 grit pad to prep it for filling the holes.

The aft two head thru-hull fittings ground down and ready to be filled with fiberglass cloth

Of course suiting up and venturing under the boat with the grinder in hand lead to the excavation of some blisters and poorly executed previous repairs , but I’ll save that for a future post.

Once all the holes were ready inside and out we added one layer of 1708 cloth to the interior.

One layer of 1708 cloth over the interior of the old galley thru-hull

We then moved outside, added a bit of thicken epoxy to the hole to avoid air bubbles, and filled the holes with between five and seven layers of 1708 cloth.  The number of layers varied depending on the thickness of the surrounding hull.

The exterior view of the old galley thru-hull

I discovered some debate as to the best method for laying up cloth to fill the old hole.  Ultimately I decided to start with the largest piece of fabric against the hull and work out to smaller pieces until reaching a relatively uniform thickness.  I believe stacking the wet cloth in this order makes it easier to avoid air bubbles trapped in the layup.

The exterior view of the old head thru-hulls

Next step will be to grind down the surplus material and fair the area back to the hull.