As you may have read in Stubborn Seacocks the in-line ball valves that were on the boat were corroded and generally unacceptable for extended blue water sailing. We are replacing all of the seacocks on the boat, a major job. After we surveyed the boat and marked down the varying sizes of the thru hulls the next major question was what type of seacock / thru hull are we going to replace all of them with? The first major decision was that no mater what brand, the seacock had to have a flange. The second decision was a little more complicated: Bronze or Marelon?
Bronze or Marelon?
First, some of you may be asking what the heck is Marelon? Well it is a mix of polymer composite compounds that a company Forespar has developed for marine use. Basically its a super strong plastic engineered with boats in mind. Hopefully you aren’t wondering what bronze is but if you are: bronze is an alloy metal dating back to the 5th millennium BCE. That’s a long time ago.
Traditionally bronze seacocks are the way to go. Period. They are suitable for the marine environment and the some of them are built to specs that make them extremely durable while offering good corrosion resistance. The best of them have rugged handles that will not bend or break when strong force is applied. Bronze has been the accepted seacock material for generations upon generations, from the old tapered plug to the stainless steel or chrome plated ball resting in PTFE. The major drawbacks of bronze seacocks are corrosion and the need for electrical bonding.
And then came new scientific developments and plastics! Just like boats were built of wood since the beginning of time until plastics showed up on the scene, so it goes with seacocks. For years many reputable boat builders and yards have been installing Marelon plastic seacocks in the fiberglass plastic boats they are producing. There are a lot of people who are skeptical of these seacocks for below the waterline use. Their arguments are usually that marelon is not as strong as bronze, there is less abrasion resistance, they can be degraded by UV rays, and that they can melt in a fire. I whole hardheartedly respect most of those concerns! But lets look a little closer: How much UV degradation are we going to get in the bilge? What exactly is going to chafe through a seacock? Marelon or bronze, I don’t make a habit of storing my hacksaw blades exposed in the bilge. As far as melting and strength, as Don Casey points out in This Old Boat, “I guess the benefit of a fireproof valve installed in a plastic boat eludes me, and as for strength, I have never seen a report of a single Marelon seacock failure other than broken handles on the smallest valves (which will not happen if you exercise the seacock).” (This Old Boat, Second Edition p334)
So, which one did we choose?
The truth is I am a traditionalist at heart and I see a lot of value in a beautiful, rugged bronze hunk of bronze in the bilge but I also am absolutely confident in modern technology and having done a lot of research into Marelon I actually feel better about the Marelon valves than I do the bronze. We have both Marelon and bronze seacocks on our Catalina, each has always worked just as well as the other and I’ve never worried about either melting, breaking, or otherwise spontaneously combusting.
For the head plumbing I chose Marelon. The Alberg 37 comes with two 1 1/4 thru hulls and one 3/4 thru hull. Since everything in our sanitation system is 1 1/2 inches I upgraded the two 1 1/4 thru hulls and kept the 3/4 toilet water in thru hull the same size. As a reminder, here is what we started with:
All three of the wood bases were rotted out and flimsy, the ball valves actually moved around when pressure was applied and the thru hull fitting on the outside was no longer securely bedded. We started out by getting rid of all the old wood and grinding down the surface around the thru hull:
We made templates of the seacocks and drew out their wood bases. The template was then used to transfer onto the marine grade plywood which we cut to size.
After the wood was cut I then drilled holes through the wood for the three bolts that the seacock would then fit onto. For these bolts I used silicon bronze carriage bolts. Carriage bolts have smooth heads but a square base at the termination of the threads into the head. The square base makes an indentation into the wood when tightened down, from then on the bolt is a sturdy post coming through the wood that will not turn as the nut is screwed on or off. The smooth head allows for the wood to be mounted without interfering. We meticulously dry fit every one before proceeding to the first squirt of epoxy!
I entirely sealed the wood in epoxy. I then ground down the underside to give it some tooth, put the bolts in place and applied thickened epoxy to the bottom. I also built up the hull in thickened epoxy and then put the seacock in place. Once in place, Erin screwed in the thru hull from the outside and we let the epoxy cure.
I wanted to apply a good amount of pressure or down pull on the base so that the thickened epoxy flowed out from the sides of the base. To do this I left the thru hull at its full length and used a less than standard fulcrum to pull the thru hull out and the seacock down:
It worked so well I have used this system with all of the subsequent thru hulls!
After all the bases were epoxied in place we removed the seacocks and gave the entire area a good epoxy barrier coat.
Notice how the handles are oriented so that,
1: they can all be independently turned without interfering with one another and,
2: they will be perfectly accessible through the small cabinet opening leading into the space under the sink.