Thru Hull fitting material

[2ndwish]

We are getting ready to haul for paint and figured I'd inspect all the thru-hulls in case thy need replacement. The seacocks are all marelon, but I don't know what the thru hull fitting material is. It is a kind of whitish plastic and may be marelon. Does anyone know what the OEM fittings are?

[Ron Hill]

2nd : That's a factory question. 

I believe that some are nylon, but not sure if all are?

[mainesail]

They should be Marelon. The Marelon thru-hulls are white, the valves & seacocks are black. Marelon is glass reinforced nylon..

Marelon however, in the manner Catalina installed them in the 80's, valve on thur-hull fitting, are VERY, VERY weak and DO NOT come anywhere close to meeting the minimum ABYC safety standards for strength.

A 3/4" valve can be snapped clean off at under 200 pounds so please be careful and do not store heavy items such as tool boxes, anchors etc. where they could slide and hit one...

[2ndwish]

Thanks for both responses. Assuming they are Marelon, is there a reason to replace them (other than the one pointed out by Mainesail)? Is there some way of determining whether they have exhausted their useful life?

We had a Rule thru hull (Marelon?) for the bilge pump break last year. The part was above the waterline and exposed to sun. A post-mortem on the part revealed that the wall had thinned substantially over the years, particularly where exposed to sunlight. Can one expect similar behavior on an unexposed part below the waterline?

[stevewitt1]

Great thread!

I had to take the strainer off my engine pickup thru hull to clear an obstruction while underway this summer and everytime I would open or shut the seacock on my head pickup/shower sump drain or deck washdown I feel uneasy with these plastic units.  My last three boats all had brass underwater fixtures.
Is replacing these a common upgrade?  
Are they reasonably easy to remove from there beveled bed?
A quick look showed going from $15 identical replacements to $XXX.00 range per thru hull. Are there affordable brass replacements somewhere?  (I don't want to sound cheap and I believe anything underwater is the place for quality)

Steve

visit us at www.ocontoyachtclub.com and www.warbirdsix.com

[Fuzzy]

Steve:  The brass thru-hulls that you are refering to are probably not brass but are bronze.  Brass will corrode
when underwater (especially salt water) where bronze is more corrosive resistant.
Larry

[stevewitt1]

Thank you Larry, I stand corrected.
Steve

[Ron Volk]

Mainesail,

You mentioned in a previous post:

'Marelon however, in the manner Catalina installed them in the 80's, valve on thur-hull fitting, are VERY, VERY weak. and DO NOT come anywhere close to meeting the minimum ABYC safety standards for strength.'

What is the difference in the way it was done, what was done in the 80's, what is done now & when was it changed?

Thanks for any details or descriptions.

[mainesail]

Mainesail,

You mentioned in a previous post:

'Marelon however, in the manner Catalina installed them in the 80's, valve on thur-hull fitting, are VERY, VERY weak. and DO NOT come anywhere close to meeting the minimum ABYC safety standards for strength.'

What is the difference in the way it was done, what was done in the 80's, what is done now & when was it changed?

Thanks for any details or descriptions.

HUGE differences in strength. In the 80's they installed a Marelon thru-hull then slapped a Marelon ball valve on it. This combination, in 3/4", fails at under 200 pounds or more than 300 pounds shy of the minimum ABYC strength requirement..

Today they use the Forespar OEM/93 series Marelon flanged seacocks. These seacocks don't fail, in 3/4", until nearly 750 pounds or 250 pounds in excess of the ABYC requirement.

[2ndwish]

So I did a little sleuthing today and found out a few things (thanks to the factory and Randy at Forespar). The thru hulls are Marelon. While there is good reason to service and replace the Marelon seacocks which has been documented on this site, there is little reason to replace the thru hull. The factory reports that the only failures have been associated with heavy objects hitting the fitting (as Mainesail described). Forespar said the working life of the thru hull might be 50 years or more. That's one thing we can take off the list. It does beg the question: Why would you use anything else?

[Les Luzar]

Wish,
It is good to know that Marelon Thru-hulls last 50 years! I guess I don't have to worry too much about this "to do" any longer. I have a friend who has a 90's Beneteau that needed all new thru-hull's a few years back. They were all made of bronze! I am glad C-34's use marelon.

[mainesail]

Wish,
It is good to know that Marelon Thru-hulls last 50 years! I guess I don't have to worry too much about this "to do" any longer. I have a friend who has a 90's Beneteau that needed all new thru-hull's a few years back. They were all made of bronze! I am glad C-34's use marelon.

Most Beneteaus & Jenneau boats, and LOTS of other EU built boats ship with BRASS because it meets the piss poor European standards/requirements.

These should NOT be confused with real BRONZE thru-hulls, valves or seacocks. I have a set of nearly 80 year old tapered cone seacocks of an 80 year old wooden boat that was re-fit. Other than some green patina they are 100% operational and suffering from no corrosion issues..

As long as Marelon is not exposed to UV it can be fine for a long while. Of course I would only have flanged Marlon seacocks on my own boats not a valve threaded to a thru-hull....

[pablosgirl]

Hi Mainsail,

So if I am reading this properly, the Marlon thru hulls are OK from an 80's boat.  It's the thread on seacckcs that Catalina used that don't meet the current ABYC standards.  Is it posiable to add Marlon flanged secocks to the existing thru hulls and what would be the proper procedure for doing this if possiable.

Paul

[2ndwish]

Since this thread popped up again, I thought I'd update our status (and sort of answer Paul's question). First Paul, Mainesail has a tutorial on his site about installing a flanged seacock aftermarket without drilling screw holes thru the hull. But... When we went to haul 2ndWish and asked the yard to replace the seacocks, they told us they will likely have to replace the thru hulls anyway. They said that more often than not the thru hull fittings turn when loosening the seacock, necessitating replacement of the whole kit and kaboodle. As it turned out, one of the two moved, the other was an easy replacement.