thru-hull problems

[s/v Ale kai]

Ale kai is a 2003 Beneteau 393 Oceanis. I recently had a faiure in my aft head sink and shower thru-hull. It seems all the manganese was eaten away and the fitting cracked and broke right at the point where it went thru the hull. My yard foreman says he gets 4 or 5 Beneteaus or Jeneaus every year that have thru-hull failures. He chalked this up "inferior bronze" used in the French fittings.

Has anyone else heard of this premature failure?

Also, I think part of the problem may be stray currents creating galvanic deterioration. Does anyone know if the fittings on a 393 (American built) are bonded or not?

Thanks for any help on this.

 

[Rick I]

Interesting. Have not had this reported so far in the 393 group with over 500 members.
http://groups.yahoo.com/group/beneteau393/

 

[Jim McD]

I have a 1999 461 (purchased 10/2009) and I had the same problem with one of my thru hulls (galley sink drain). I did a little research on bronze fittings and galvanic corrosion. If you look at your seacocks/valves, there should be a #8 bare copper wire (to a suitable ground) if they are bonded. My boat was not, and every other Beneteau owner I talked with did not have a bonding system on their boat.

The decision you have to make is to replace the bronze thru hull with the same thing and add a bonding system ($$$+) and a galvanic isolator ($) on your shore power, or do something else. This seemed to me like putting a band aid on something that could potentially sink my boat, so I replaced all the thru hulls on my boat (15) with Marelon thru hulls and all new Marelon seacocks. All hoses were replaced as part of the refit (including all new holding tanks, toilets, etc.).

I am very happy with the Marelon thru hulls/valves and I think it is a vast improvement on the OEM equipment. This also gave me an opportunity to reroute some of the hoses for better accessibility and future repair/replacement (waste hoses etc.).

You can find out about Marelon thru hulls and valves here: http://www.forespar.com/marelon-marine-boat-plumbing.shtml

Hope this helps. Please feel free to contact me if you need more info.

Jim

 

[Gunni]

Where did you get the idea that your bronze thru-hulls were manganese alloy? Was it the same yard guy who told you that Beneteau's were built with "inferior bronze". I'd bet you dollars to donuts your thru-hulls are made in the USA where your boat was built. Mine are Conbracos, and Grocos. I've never seen a bonded Beneteau, or am convinced that bonding is the way to go. I'm also skeptical of plastic thru-hulls, but hey, I'm old.

 

[larryw]

I had to replace every thru-hull in the boat. The marina was old and had a lot stray current in the water. I went thru zincs like hotcakes and with the boat hauled, it was noted the bronze thru-hulls had a pink caste to them (galvanic corrosion). they were all weak and brittle. the marina was rebuilt and now a zinc lasts for six months.

 

[Jim McD]

Just curious, Larry... did you replace your thru hulls with bronze? Did you do anything about a galvanic isolator? Are you in Shoreline or Alamitos Bay?

Jim

 

[larryw]

Jim, didn't see this until today-
I went with bronze. Did nothing about an isolator since the Shoreline Marina rebuild ended the problem. Beneteaus have only one zinc, on the prop hub, and it lasts a long time now. I thought about suing Long Beach for the $4k it cost, but... Live and learn. I'm on the hard now, dealing with a shaft problem.

 

[DougM]

I'm in fresh water and have not had that kind of thru hull failure. What I did have was a sink drain thru hull freeze and split wide open in winter storage because the ball valve was left in the closed position after the yard winterized the boat, My boat is in its sixth season and the thru hulls show no signs of corrosion. the zincs still look like new. I know i should have manganese but haven't been able to locate any.

 

[s/v Ale kai]

Thanks for all the input. 'Ale kai is in Westpoint Marina, South San Francisco Bay. She was in Redwood City Marina which is known to cause boats to go through zincs like hotcakes. But apparently I'm still having galvanic problems. The drain valve on the oil cooler of my Yanmar 4JH3E just fell off at the braise point due to galvanic corrosion. I had to replace the whole oil cooler ($700 parts and lots of cursing at Yanmar engineers). None of my thru-hulls are bonded. I'm considering doing that myself. I'm hiring an independent nautical electrician to come out and check out my marina and boat to help me figure this out. Marlon doesn't seem to be a solution because several fittings have so much weight on them that I've been advised marlon would break under the pressure (two stopcocks going into a "T" for one thru-hull). BTW, if you ever need to change the oil cooler, buy a 36" breaker bar and a 27mm socket. They will save you hours and broken knuckles.

 

[Gunni]

Have you installed a galvanic isolator on your boat? Start there before you pay a consultant to analyze your marina. It is an easy, cost effective DIY project. Resist the urge to bond your through-hulls.