Galley Sink Seawater Thru Hull

• Action: To Do List item A0077 – Obtain and replace galley sink seawater intake thru hull, seacock, clamps, and hose.
• Action: To Do List item B0160 – Obtain spare Whale Gusher Galley Mk3 Service Kit P/N AK0553.
• Completed:  8 April 2017
• Cost: $408.58

The reasons to replace the galley sink seawater intake thru hull were due to the installation of a non-marine rated Philmac blue handled 3/4 inch ball valve seacock, plastic thru hull of unknown manufacture and material, and use of non-marine rated hose for a below the waterline location.

Use of seawater for cleaning and washing at the galley sink was a common practice that reduces the use of fresh water as revealed on review of multiple boating/blogging internet websites, so this installation concept was retained.  The Whale Gusher Mk3 Manual Galley Foot Pump installed was a currently produced item with downloadable documentation and had a service kit for repairs that was also ordered.  In regards to the choice of bronze or plastic for thru hull and seacocks - we choose items made of bronze by Groco due to the incomparable strength of bronze, flanged mounts, backing plates, quality, and reputation.

Determining what needed to be ordered required a complete detailed plan and list, as items were planned to be purchased mostly over the internet at US websites, shipped to and consolidated at a freight forwarder in California, and then shipped by ocean freight to our location in the Philippines - a two to three month process.  The lack of identifying a needed part would entail an additional two to three month delay.  So the plan started with the facts of what was known - the thru hull hole was 3/4 inch, the Whale Gusher manual pump ports where 1/2 inch, and the faucet attachment was a 1/2 inch hose barb.  The selection of a bronze thru hull of 3/4 inch size drove the need for a compatible sized backing block, a 3/4 inch flanged adapter with bronze bolts and washers, and 3/4 inch seacock.  This in turn drove the requirement for a 3/4 inch to 1/2 inch adapter to fit a 1/2 inch threaded adapter with 1/2 inch size hose barb.  The 1/2 inch hose selected was marine rated and approved, a Trident heavy duty water hose that exceeds SAE J20R3 standards.  Next issue was, what size clamps were needed?  The 20.7 mm outside diameter of the 1/2 inch hose determined the size of clamps needed.  AWAB clamps were chosen due to their quality construction in all 316 stainless steel. The AWAB SEA size 8 clamp had a clamping range of 15 to 24 mm which would fit the hose's outside diameter.  Two clamps at each hose connection were to be utilized, but not due to regulatory or ABYC recommendations which stipulated only one clamp needed, but due to practical common safety sense.  Last item considered was a external strainer to minimize unwanted material pumped in with the seawater and reduce the possibility of material clogging the inlet - it needed to be a hinged type strainer as review of fixed strainers revealed they were extremely difficult to clean and remove any barnacle attachments, especially on internal exposed surfaces.  The removal of the existing plastic thru hull and installation of the new items was envisioned to determine what else might be needed.  Review of internet websites and videos provided lots of advice and suggestions - some worthy of review and mention, Marine How To website and Capt. Wayne Canning videos.  The installation of the backing block would need epoxy mixed with a filler, a sealant rated for under the water line locations was needed to seal the thru hull, flanged adapter, and screw holes.  The threaded connections would need to be sealed with tape.  Surfaces needed preparation by sanding; then it would be prudent to protect any bare surface with a barrier paint coat. Screws to be installed would need a starter hole, so a drill with bits was needed.

A pictorial diagram depicting the complete system was created to identify and illustrated the parts and material needed.

The following items were ordered and received by ocean freight shipment.

Access to the seawater intake thru hull was through a galley corner cabinet door that due to its small entry restricted use to one arm/hand.  This lack of access is the reason this was the first thru hull to be replaced - do the perceived hardest and most difficult task first - so doubts are removed, confidence grows, and the remaining tasks then seem trivial.  The hoses to the Whale Gusher manual pump were removed first and then the pump, but only slightly improved access.  The clamp and hose were removed from the seawater thru hull; and with difficulty, the plastic thru hull nut was removed using an adjustable wrench, a quarter turn at a time.  Surprisingly, two blows from a sledge hammer knocked the thru hull loose enabling it's relatively easy removal.  What takes a few words to describe, actually consumed about three hours to accomplish - as the old expression confirms, time flies when your having fun.

What was believed to be a 3/4 inch hole turned out to be just slightly less as the new Groco 3/4 inch thru hull would not slide into the hole.  Used a Dremel rotary tool with a barrel sander attachment to sand and enlarge the interior of the hole.  All the new pieces were assembled and dry-fit installed to determine surface irregularities and alignment of the seacock handle for easiest movement and access.

Measurement of the hull thickness at the hole was just over 3/4 inch.  The Groco hinged strainer was aligned and pilot holes for attachment screws were drilled.  These pilot holes completely penetrated the hull, but were not a concern as the backing block for the seacock mount flange would be mounted over them on the interior sealed with epoxy.  Based on the 1 inch length of the strainer mount screws when positioned in the strainer mount holes, it was estimated their length would still penetrate the hull by about 1/8 inch; driving the need to re-drill the holes after the backing block was epoxied in place.

The mount surface of the Groco backing block, and exterior and interior surfaces were sanded with 80 grit sandpaper and the area wiped clean.  The base of the brass nuts on the Groco backing block were covered with a small piece of masking tape in the hopes of preventing the epoxy from oozing up onto the threads.  A small batch of West Systems Epoxy 105 and 206 was mixed and thickened with MAS Epoxies colloidal silica and applied to the Groco backing block and interior hull mount surface.  The Groco backing block was aligned with the previously applied mark indicating top and set against the hull.  The epoxy oozed up through the three unused holes and was scraped off.  The Groco flange adapter was mounted to the backing block with the three brass bolts and washers; and the thru hull with masking tape on the threads was installed and tightened.  The excess epoxy was contoured around the outside of the Groco backing block and all was left to cure.  After about an hour, removed the thru hull and flanged adapter.  Despite precautions, the epoxy was still able to coat the thru hull and brass bolt and nut threads; requiring additional effort to clean the threads - would need to rethink this method as more thru hull backing blocks remained to be installed.   Two coats of Interlux InterProtect HS Epoxy Primer (YPA422 / YPA420) were applied to the exterior and interior surfaces and allowed to cure dry.  All the new items were reinstalled again, dry-fitted, to verify fit and alignment, before final installation with the application of sealant.

One final dry fit and 3M 4200 Marine Adhesive sealant was applied to complete the installation of the thru hull.