You're absolutely correct that with the Forespar product you'll have no electrolysis
problems. From the pictures, it looks like you got one of the Chinese Groco ball valves. Groco, unlike Forespar re. Catalina
, has put out a bulletin regarding their problems.
My boat was in the Caribbean
for close to 10 years and when I sold it 4 years ago, all the thru-hulls were in excellent working condition. They were Apollo flanged seacocks. I'm not endorsing Apollo by any means. So it appears that you've got a defective product or have a serious stray current
issue, or both.
All I did was provide you with the facts about Marelon and the 93 design. I leave it up to you as to what you do with it. The weakest point on your boat will now be the 15 nylon nuts that the handle bolt screws into. I can say that from a molding perspective those nut threads are 98% straight nylon and after a few months in the warm Caribbean
waters will be saturated and the threads will be very soft. My suggestion is to always open or close the valves using a straight line pressure on the handle, any serious pressure on the handle away from the valve can strip the threads, see the Catalina
bulletin. Also, the safest position for the handle, impact wise, is in the open position.
I'm curious, did you end up replacing the 1/2" for a 3/4" and did you keep the 3/4" size valves or go to 1".
Marelon is nothing more than Dupont's standard Zytel nylon 66 with a 13% glass loading. A 1930's plastic material with a little glass thrown in for strength, not what one would call "space aged." The Concorde (1969), when compared to Marelon, is truly "space aged."
Regarding the Concord analogy, you state "I have a plastic boat so why not plastic thu hulls/sea-cocks" I couldn't agree more. In fact, I can tell you of several plastic materials that exceed all the ABYC/UL criteria by a country mile, even when saturated in water
. Here are two pictures of a Marelon tailpiece and a tailpiece made of one of those plastics. Since you stated, "I am going with the flush thru hulls so no worries about wiping out a plastic fitting that is proud of the hull
surface." it's obvious that impact is a concern of yours. As you'll see the Marelon tailpiece was wiped out in 2 hits using only 3 ft of gravity and an 8 lb weight. The other material tailpiece lasted 18 hits and, while cracked would still get you home. So, YES, I agree a plastic boat should have a plastic thru-hull and seacock. I just don't think 1930 technology nylon is the appropriate material. It is, however, cheap
and easy to mold
Dave, I hope we do hear from you on this forum and that the no situation arises in your cruising that will cause the problem to reveal itself.