Marelon Thru Hull Fittings

[hikersailor]

I will be replacing all my thru hills about 8 or so as the vessel is a 99" and I do not trust what condition they may be in. Any input on the use of Marelon for thru hull fittings and ball valves versus bronze? I know Marelon will have not issues with corrision/electrolysis and they are about half the cost and meet the marine industry requirements for underwater use.

[Stumble]

I don't trust them for below the waterline. At least the last time I looked they didn't meet the standards for ABYC, but I could be wrong. Even if they are certified, I still wouldn't use them. Groco bronze will last for the rest of your life, and likely longer.

[knottybuoyz]

Load Testing A 3/4" Marelon Ball Valve & Thru-Hull Fitting - YouTube

[HopCar]

There are a lot of boats out there with Marlon fittings and most are still floating.
Just Kidding! I've never heard of a boat sunk by the failure of a Marlon fitting. I do prefer bronze.

One point I'd like to make is the difference between a ball valve and a seacock.
A proper seacock has a mounting flange and a ball valve doesn't. I, and a lot of smarter people, think it is dangerous to just screw a ball valve on a thru-hull fitting.

You should use a flanged seacock that is mounted to the hull.


Groco Full-Flow Flanged Ball-Type Seacocks FBV750-2000


Groco Full Flow In-Line Ball Valves (IBV series)

[Cheechako]

Yeah, what he said. What do you have now? Why do you think they are bad? Marelon is tuff stuff, but some details fail in my experience (one boat)

[Rhapsody-NS27]

I've replaced one OLD valve/thru-hull and have several more to do using Maine Sail's instructions on his site. He has a few pages on this topic. Here's one of them.

www.pbase.com/mainecruising/replacing_thruhulls

[colemj]

If you decide on Marelon (Forespar), only get there OEM series. I think it is the 93-series or something like that. These won't be for sale at the local chandlery and you will have to order them. But they are way above the common ones in terms of quality and construction.

I can't imagine that they are not ABYC compliant, as many manufacturers install them as standard.

We have them for all thruhulls. I have never heard of a sistership having any problems with them.

Mark

[CarlF]

Yes. If you want to use marelon for a seacock, the Forespar OEM 93 is the one to get. It is vastly superior to the other Forespar type. Here's Maine Sail's video showing it easily passing the ABYC test.

https://www.youtube.com/watch?v=SLvLKnzop-0

I've also never heard of one of the OEM 93 series breaking their handle (a real problem with the other design). And finally, they don't seems to require lubrication (although Forespar recommends it). I just exercise mine a couple of times a year. After 10 years the operation is as smooth as when the boat was new.

One caution, the opening is slightly undersized because of the thickness of the thru-hull wall. Many use a 1" OEM 93 where they might use a 3/4" in bronze.

[Scott Berg]

Definitely Marlon meets all ABYC rec's


Sent from my iPhone using Cruisers Sailing Forum

[hikersailor]

In reference to why do I think mine are bad I can only judge from the external appearance which is not much of a confidence builder and stiffness of operation plus they are 15 years old and I do not like the fact that they are installed with the thru hull and nut against the inner hull with a ball valve on top of that. There should be a backing plate. You can mount a separate ball valve on a flanged base as Groco makes which would aallow one to replace the valve later without having to remove the thru hull. I was unaware of the 93 series that are more robust Marelon products so I wiill take a look at that. Marelon is industry approved for thru hull underwater applications. Thanks for the replies.

[botanybay]

If I remember correctly, do not use them on on wooden hulls, the expansion of the wood can break them (or at least the through hull fitting itself).

[hikersailor]

My application is a '99 Leopard catamaran so wood will not ba an issue.

[thinwater]

What do we have regarding Marlon and deterioration over time? The plastic would no be affected by seawater exposure and there is no UV. I've tested 30-year old nylon rope that has been out of the sun; loss in strength is barely measurable. We know the FRP does not really age, unless flex or UV are involved.

Clearly there could be fatigue from use or abuse, but is there any engineering basis for replacement? If the fitting was protected from impact, it may be absolutely no different from new. That is what I have observed on Marlon fittings of that age range. Not sayin' you can't replace something in the search for peace of mind, but whether that should be in one year or 40 is a tough question. With bronze and brass the effects of time are more visible.

I'd be inclined to simply give them a really good inspection, including the handles.

[botanybay]

Originally Posted by hikersailor

My application is a '99 Leopard catamaran so wood will not ba an issue.

Definitely do not use wood or plywood backing plates with them either. Same issue.

[Cheechako]

Originally Posted by thinwater

What do we have regarding Marlon and deterioration over time? The plastic would no be affected by seawater exposure and there is no UV. I've tested 30-year old nylon rope that has been out of the sun; loss in strength is barely measurable. We know the FRP does not really age, unless flex or UV are involved.

Clearly there could be fatigue from use or abuse, but is there any engineering basis for replacement? If the fitting was protected from impact, it may be absolutely no different from new. That is what I have observed on Marlon fittings of that age range. Not sayin' you can't replace something in the search for peace of mind, but whether that should be in one year or 40 is a tough question. With bronze and brass the effects of time are more visible.

I'd be inclined to simply give them a really good inspection, including the handles.

Regarding Nylon (not Marelon) I've had nylon thru hulls (bilge pump ones) crumble into pieces or break trying to get a hose on them. These were exposed to the sun.
I know that many plastics have issues with swelling over time, not sure if this is why the Marelon ones tighten up and the handles break or not.