I guess if one was reeeeeeeaaaaaaalllllly into racing, a recessed mushroom head would cut your drag way down
. Almost as much as cutting you toothbrush in half to reduce your weight.
Marelon Seacock fail!
- Thread starter Hayden Watson
- Start date
. Almost as much as cutting you toothbrush in half to reduce your weight.
Many years ago, when the series 93 ForeSpar valve was a new idea, we replaced all of our 1988 OEM Marlon valves that were screwed onto marlon thruhulls. That was in the late 90's.
We used the '93" assemblies. With an frp backing plate inside, the valve body was drawn up tight with the outside threaded part. Seated the whole thing - in and outside - in thickened epoxy. Once hardened, the outside flanges were all ground off flush.
No leaks, and strong as Heck.
While there are other ways to bed these into place, I see no reason to rely on sealants or tape. Decades in the future when you replace them again, you will just run a hole saw (drill) in from the outside and start over.
Certainly not the only answer, but often there are several 'right' ways to approach these things.
Also: the headline is indeed misleading.
We used the '93" assemblies. With an frp backing plate inside, the valve body was drawn up tight with the outside threaded part. Seated the whole thing - in and outside - in thickened epoxy. Once hardened, the outside flanges were all ground off flush.
No leaks, and strong as Heck.
While there are other ways to bed these into place, I see no reason to rely on sealants or tape. Decades in the future when you replace them again, you will just run a hole saw (drill) in from the outside and start over.
Certainly not the only answer, but often there are several 'right' ways to approach these things.
Also: the headline is indeed misleading.
@Ralph Johnstone You are "reeeeeeeaaaaaaalllllly" missing the point.I guess if one was reeeeeeeaaaaaaalllllly into racing, a recessed mushroom head would cut your drag way down
Almost as much as cutting you toothbrush in half to reduce your weight.
The boat's hull HAS a 2½"ø by 3/8" deep recess CAST into the hull that the OEM recessed thru-hulls are mounted in. The threads on those recessed thru-hulls are PSM parallel thread form (American Standard Straight Mechanical Pipe Thread) which is not compatible with the buttress threads on the Marelon flanged seacock.
Given that the flanged seacock's buttress threads can not be threaded onto any thru-hull that will fill the recess that is cast into the hull in the mold, I had three options.
- use an OEM ball valve with PSM but has no flange and does not meet ABYC standards for below water thru-hull/seacock due to lack of strength.
- remove the recess and fill it back to flush. To do this properly would require grinding a 12" diameter depression at 12-1 and filling it with 3/8" of resin and cloth then drilling a new hole for a mushroom head.
- Deal with the recess as I did by mounting the mushroom head at the bottom of the recess which was so big that the full mushroom head of the thru-hull fit against the flat at the bottom of the recess with room to spare.
In hind sight, I wish that I also had ignored the Forespar instructions and the assurances of the Marelon tech rep and used something other than Teflon Tape because now it will take another haul out to fix the stupid nascence leak in what should otherwise be a dry boat.
And yes, this is a FAIL of a Marelon seacock. I did not title the post "Marelon seacock FAILURE" This is a fail in the installation but the name Marelon is to be associated with that FAIL because their installation procedure was followed to the letter and that is where the fail happened.
Note to self, screw Forespar's instructions and never use Teflon tape to install a Marelon flanged thru-hull. Hopefully others will benifit from my FAIL and ovoid one of their own.
Also in hind sight, I REALLY wish that I had been able to find the TrueDesign seacocks that I wanted to install, because they would have bolted right up to the OEM thru-hull with PSM threads.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,503
yep, with the load bearing collars.
My point was/is, what the hell is the function of a recessed thru hull on the exterior of the hull in the original design ? ? ? ?
I'm guessing it's for reduced drag which in truth would be negligible compared to a standard, protruding mushroom head. Unless one was to achieve extreme, never before heard of speeds in a sailboat.
Makes good advertising I suppose.
One does not generally use the phrase, "extreme, never before never before heard of speeds in a sailboat" and "Catalina" (or "Hunter," for that matter) in the same sentence.
Yes I see what you mean.
It smacks of a certain dissonance now that I see it layed out before me
.
@Hayden Watson , I'd name this thread "Forespar Fail". Apparently their Tech Support doesn't know there is a reason the installation instructions for the Series 93 OEM Valves with buttress threads do not include "teflon tape" as a sealant on the buttress threads.
I limited my criticism of Forespar to their Marelon division because I have no beef with the rest of Forespar, just the Marelon tech and their written instructions. My hope is two-fold.
- That Forespar will read these posts and the multiple comments from others about not using Teflon tape for this connection and change their stupid instruction to something that has a better chance of working.
- That other boaters will stumble across this thread and thereby avoid going down the Teflon trail to destruction.
Yes, and no. More a case of insufficient instructions.
Marelon said no aggressive sealant, by which they meant a locking type (they specified "removable"). They said Teflon tape was a possibility, but did not specify it. What color did you use? How many turns? It matters, but they did not specify. This assumes user experience. For a non-standard application like this, they should have specified color (they are different thicknesses--most people mistakenly use white tape for larger fittings, for which it is not designed) and number of layers. Pink or yellow and about 3 layers would be normal for this range of sizes.
The instructions were poor, but any experienced pipefitter would have chosen a paste sealant for running threads. It does not sound like the Marelon fitting was defective, only installed incorrectly, and straight threads are tricky this way. I have installed dozens without a leak. Of course, I've installed thousands of pipe fittings over the years.
Poor instructions and the assumption that folks are experienced. They probably assume that most are pro installed.
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I might consent those points but I contacted the Tech rep for Marelon at Forespar.com and he told me that Teflon tape was their "preferred" sealant. I was inclined to use a paste pipe dope but he convinced me to go with Teflon. It is a FAIL on the part of the Marelon division at Forespar was regards their published installation instructions and should be changed.
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Why not just name the thread "Teflon Phhhhhhtttttttttt".
Because it is not a problem with Teflon tape. It was following Marelon's instructions that lead to the fail. If I had not read the instructions, I would have sealed the whole mess with 4000UV and been done with it. But given the importance of a seacock, I decided to read the instructions so that I would "do it right" and that lead to the problems. It is not the Teflon tapes fault, it is Forespar's fault for recommending its use. They have printed documents available on their web site that tell you to use Teflon. I cannot blame Teflon tape for Forespar telling their customers to use a product that is not suitable.
That I agree with completely. Terrible guidance.
What color Teflon tape did you use? Yes, it makes a difference. In may areas, on land, the wrong tape will fail a code inspection.
thinwater: It was water plumbing white on a blue spool with white cover. Teflon branded manufactured by Chemours.
Ralph Johnstone: is it not pickiness or semantics. Chemours, the manufacturer of Teflon did not recommend to me that I use their product so why would I say that their product failed. They did not proved the failed instructions. The Fail must be attributed to the Marelon division of Forespar because they are the ones who give the instructions on how to install the Marelon products and which sealant to use on the different components.
Ralph Johnstone: is it not pickiness or semantics. Chemours, the manufacturer of Teflon did not recommend to me that I use their product so why would I say that their product failed. They did not proved the failed instructions. The Fail must be attributed to the Marelon division of Forespar because they are the ones who give the instructions on how to install the Marelon products and which sealant to use on the different components.