Replacing in-line valves with seacocks
Two of the five thru-hulls on Freya had been re-plumbed with in-line ball valves by previous owners (the factory installation relied on Spartan bronze seacocks everywhere). As noted by Maine Sail in this excellent article, using in-line valves on thru-hulls is usually not a great idea, mostly for two reasons: 1) the threads are often incompatible (NPS on thru-hulls, NPT on valves), resulting in a very poor fit (three or four threads at most); 2) compounding the previous issue, the lack of a flange on in-line valves means that nothing prevents them from twisting (and eventually disconnecting from the thru-hull) when turning the handle.
The above would have been good enough reasons to replace the valves but in Freya‘s case, there was another: at least one of the two valves was made of cheap brass. The risk of de-zincification, coupled with the issues inherent to in-line valves, made me wary enough to schedule a quick haul-out to replace both. There was a spare, new Spartan bronze seacock identical to those used at the factory stored in one of the boat’s lockers (evidence that another owner was aware of the problem?) – I decided to use it for the engine intake. For the head, I went with a newer model from Groco (BV-750), also made of bronze.
I worked in tandem with one of Svenden’s employees to replace both valves in about 4 hours. The process was reasonably smooth: removal of the old thru-hulls, dry-fitting of new thru-hulls and seacocks, cutting of the thru-hulls to size, drilling of additional holes for the flange bolts in the head, final assembly using copious amounts of 3M 4200 fast-cure to seal everything. The pictures below document most of the process. You’ll be able to see how thick the hull is in these areas, and also how it is further reinforced with glassed-in backing plates (meaning I did not have to install any, a significant time saver). Yet more evidence that Cape Dory knew how to build quality boats.
- Note the CW617N stamp, clearly indicating the valve is made of “Tonval” brass.
- It is quite likely this valve was made of bronze. It still had the issues associated with in-line designs though.
- A proper bronze seacock, identical to the ones installed at the factory.
- Hanging in the slings for the day.
- Exterior view of the engine intake (thru-hull is behind strainer).
- The removed strainer. Turns out it was held only by sealant, the screw heads were gone (probably destroyed when the old seacock was removed by the PO)…
- The engine intake thru-hull (you can see the headless screws for the strainer…).
- Thru-hull removed. Note how thick the glass is.
- Thru-hull removed from head intake. Very thick glass in this area also.
- If you look closely, you can already see evidence of de-zincification (reddish areas near the base).
- This valve was held by about four threads… it could have been worse, actually.
- No de-zincification here. However, this valve was held by only three threads!
- The mounting pad for the engine intake seacock. The original holes for the flange bolts were still there, ready to be re-used.
- The new head seacock during dry-fitting.
- The new head seacock, fully installed.
- The engine seacock, installed and ready to go.
- Strainer reinstalled over thru-hull, with proper screws this time…
- The new head intake thru-hull.