rwindman - Everything i've stated is a fact.
Cotemar - I know that there are boaters out there with 50 year old non-functional gate valved seacocks, who have never had a problem with them. I'm sure the same is true for the Groco seacocks that had corroded balls and stems who are still out there and will tell you they've never had a problem. There are quite a few boat owners with the 93 series, that like you never had a problem with their seacocks, until the latent problem they really had decided to make its presence known.
Everythng! These aren't claims, they are indeed facts.
Nine years ago I thought Marelon (AKA Dupont Zytel 70G13L) was the gold standard for marine plastics. Actually tried molding a marine fitting with the 70G13L (AKA Marelon.) I assumed that the ABYC knew what it was doing. It was a bad assumption.
I wasn't getting the precision out of the "Marelon" so another material was suggested, the material had virtually no mold
shrink and worked perfectly. Before I dared re-do the molds I wanted to compare it with "Marelon" (the gold standard) for strength. The numbers I presented above are the correct values for Marelon (AKA Dupont Zytel) right off the data table.
Marelon does loose over 60% of it's tensile strength and flexural modulus within months of being immersed in water. Actually, in a marine environment Marelon will have loose 57% of its tensile strength and 64% of its flexural modulus. And those are the facts direct from Dupont and Forespar.
Actually, those aren't completely the facts, because I discovered only a year ago that according to Forespar, in their ABYC/UL documentation
, there appear to be not one but TWO "Marelons." The thru-hulls accordng to Forespar are made of a different Dupont nylon material called Dupont 8018. Yes, TWO Marelons.
The thru-hull 8018 Marelon has a tensile strength of 12,900psi and a flexural modulus of 530,000psi and will loose 55% of its tensile strength and 61% of its flexural modulus in a marine environment.
So I wasn't quite truthful. The Marelon 93 thru-hull, in a marine environment is only 81% as strong as PVC (tensile strength) and just over half (48%) as strong as PVC (flexural modulus.)
So how does the ABYC and Forespar get around these facts? As I've said before, somebody decided that the non-metal material used in thru-hulls and seacocks should be tested, "DRY AS MOLDED."
So here's a few WHY'S? for anyone reading this to ask themselves.
1. Why would you set a material standard for a critical below the waterline product as "DRY AS MOLDED?" I'll give you a hint, I asked ABYC this question, and I'm still asking it.
2. Why did Forespar make the 93 series thru-hull fittings oversized? And why didn't they do the same for the 849 series, the ones that you and I can buy?
3. The 93 series has 6 sizes, why did they make the thru-hulls non-standard so that if a boat owner wanted to replace the seacock/thru-hulls with bronze would have to re-glass the oversized holes for every odd sized (1,3,5) 93 series unit? By the way, the even sized units all have a diminished flow rate. For example, the 2" thru-hull only has the flow rate of the 1.5" unit.
4. Why do the 93 series handles fall off so easily? And why can the 93 series flood your boat once the handle has fallen off?
There's a lot more to this than I've mentioned here. I stumbled on to this, I feel, serious issue solely by chance as I said some years ago. I can't answer for the ABYC and why they did what they did, from what they've provided me for answers neither do they. So I've tried to provide some honest information on the issue.
I really would like some thoughtful responses to what I've presented. What is it you'd like to see regarding thru-hull and seacock characteristics?