S/V Johanna Rose: New Thru-hulls and Seacocks

Old Thru-hulls & Seacocks

When I purchased the Johanna Rose, I had to transport this engineless vessel over 130 NM home to my marina. I did not dare touch any of these seacocks for fear of disaster. once hauled out of the water, I was glad to first remove the old thru-hulls, decaying seacocks, and cheap hose which were used for under the waterline scupper drains(see photos).

A concern with with any cored hull boat is water intruding into the core and leading ultimately to delamination. The Johanna Rose exhibited no signs of wet core as she tapped out solid all around, had no signs of blistering (other than over the lead keel, see post on bottom work), and did not weep during the many months on the the hard. But the first real concern and test was in removing the old thru-hulls. Old leaky thru-hulls have been know to cause wet core problems. On the LF38, which is cored with end grained balsa ever where except for regions where thru-hulls are located. In this area the core is marine grade plywood. the Johanna Rose has 8 under water thru-hulls: 2 in the galley, 3 in the head, and 3 in the engine well. I removed all thru-hulls with a tool I borrowed from the marina. Upon inspection of the inner core, I found no wetness or indications that thru-hulls were leaking. This was a great news.

removing old thru-hull

a close up view of the engine water intake seacock
& port scupper seacock

old seacocks in the engine well, notice the quality hose

NEW Thru-hulls & Seacocks

thru-hulls

(2) 3/4” Groco FTH-750
(1) 3/4” Groco TH-750
(3) 1-1/2” Groco FTH-1500
(2) 3/4" Groco THXL-750-W

seacocks

(5) 3/4” Groco FBV-750
(3) 1-1/2” Groco FBV-1500

Reaming Back the Core and Filling with Thickened Epoxy

The plywood core was reamed back from the thru-hull hole using a Dremel and a sanding drum following the procedure illustrated by Wally Bryant on the Stella Blue site. The seacock boltholes were over drilled to expose clean fiberglass. A coat of Johnson Paste Wax was applied to a thru-hull so that a thru-hull inserted into curing epoxy would release easily. These thru-hulls were inserted with thickened epoxy to fill the inner reamed out area and a proper faired flush mount fit. The reamed out area and the boltholes were first wetted with epoxy before being generously filled with epoxy thickened with colloidal silica.

thru-hull in galley near keel stub

The Installation

The seacocks are mounted to backing plates made from a 1/2" sheet of structural fiberglass (FRP). These FRP mounting plates are first aligned using a tightened thru-hull, marked, and then epoxied to the hull after grinding a clean surface. The hull and backing plates are first coated with wet epoxy and then coated with epoxy thicken with colloidal silica and finishing with a fillet of thickened epoxy along the backing plate circumference. Care was taken so that epoxy would not interfere with the seacocks threads, but just to get certain, a tightened waxed thru-hull remained in place while the epoxy cured. Prior to final installation, the thru-hulls were removed, soaked in Naphtha to dissolve the wax. With the seacocks firmly epoxied to the hull, the thru-hulls were installed using plenty of adhesive/sealant. after which the area is cleaned, sanded, and lightly faired with thickened epoxy.

Seacocks