Replace Plastic Through-Hulls?

[Sailing Steve]

We have our newly purchased C34 out of the water to have the bronze prop shaft replaced because it is fairly pitted.  The boat yard has stated that the existing plastic through-hulls are "garbage" and should be replaced with bronze.  Is this sound advice, or am I being fed a bit of a line.  The surveyor never indicated that plastic was a problem and all but one function just fine.  Obviously the one that is seized must be replaced regardless.

Thanks,
Steve

'90 C34 L'Abri
Hull# 1080

[Ron Hill]

Steve : Sounds as though that boat has been around a bunch of stray current(maybe no Zn!).  Lucky that it didn't have bronze thru hulls or they'd look like the shaft you're replacing!! 
The marelon thru hulls are not "garbage"or"plastic", but like any thru hull must be greased and exercised periodically!!  Sounds like the surveyor didn't check ALL of the thru hulls and missed the obvious!   

[Stu Jackson]

Keep 'em.

Do a search on Marelon -- you'll learn a lot.  Plastic is different than Marelon.  M is OK, pl is NOT.

BTW, ours are doiong fine after 20 years!

[Sailing Steve]

Thanks for the pointers - didn't know that they were not a simple "plastic" and yes, the surveyor obviously didn't check all of them, or at least neglected to mention one was seized - hmmmm.  The prop shaft we knew about, so at least it wasn't a surprise.

Steve

[Randy and Mary Davison]

Steve,

The 1/2 inch Marelon stopcocks are especially prone to sieze if they aren't lubricated every six months or better as mentioned in their instructions.  Just turning them every few weeks isn't enough.  I've had two sieze up and now pull the hoses off and grease them with Lanocote two or three times  a season of if they become stiff at all.

[Ron Hill]

Randy : You are sooo correct. 
Most of the thru hulls only turn 90 degrees, so it's important that the top (closed) and the bottom (closed) of each valve are lubed.  Otherwise you've only lubed 1/2 of the ball valve.   

[sail4dale]

OK, I'll plead ignorance and ask:  How do you lube the valves while in the water?   I can see taking the hose off when the valve is closed will allow lubing the top but  ????? the bottom??

Also, is Marelon what is currently being used or have there been some changes over the years?

[Ron Hill]

Dale : You have to be out of the water to lube the "bottom" and the "top".  In the water you can only lube the "top"!!
Catalina has always used Marelon thru hulls on the C34 since 1986.   

[Randy and Mary Davison]

Ron,

A thought on lubing the through-hulls.  I've had them freeze even after lubing them from the top regularly.  Some folks use vegetable oil to lube them.  I suppose you could pour enough veggie oil down the hose to put the entire ball assembly in oil and then exercise it until it's thoroughly lubed.  What do you think?  What might be a better lube to use that's a fluid?

[Stu Jackson]

White lithium grease spray

[Randy and Mary Davison]

Hi Stu,

the veggie oil idea is for doing it while the boat's in the water:  Buy a gallon of cheap vegatable oil at Costco, put a hose long enough to reach above the water line, pour in oil to displace water in the hose, operate valve 20 times.

Maybe not worth the mess...I'm going to try it on one of the sinks next time a valve gets sticky as the long hose is already in place.  We only pull the boat every two years.

[Susan Ray]

Won't the oil float on water? not displace it? Let us know if it works.  I'm starting to get worried now as I haven't done anything but move the valves on the thru holes.

[Gary Ambrose]

The following is a cut and paste from <www.marelon.com> on thru-hull fittings/maintenance. 

It seems as if sometimes, in our efforts to be good cautious sailors, that we drive ourselves to a place where we do not trust our C 34's. 

MAINTENANCE:
FORESPAR® MARELON® Thru-hull/seacocks are corrosion free and provide great peace of mind in that regard. They are relatively maintenance free. Generally, lubrication is not required. What is required is to open and close them on a regular basis (4 times a year minimum). The frequency this is required is determined by two (2) things, whether the valves are routinely kept open or closed, and the rate of sea growth (weed and barnacles) in your area. If the rate of fouling is high and the valves are not actuated regularly, this build up of growth can cause any valve to turn hard or not at all. If the valve becomes stiff due to lack of use and sea growth build-up, it must be cleaned. The restriction of flow into the valve may cause harm to the machinery it serves and the valve may seize if not maintained. DO NOT DISASSEMBLE VALVE OR LOOSEN BOLTS EXCEPT IN EXTREME EMERGENCIES. All valves are factory pressure tested before shipping. Any adjustments to the bolts will void this testing and may void warranties.

[Randy and Mary Davison]

Don't believe everything you read - especially ad copy!   I just replaced two - one frozen and one amost so.  We keep the boat in the water and pull it every two years for bottom work, turn the valves at intervals of no longer than two weeks all year, and lube them from the top regularly.  Our fouling rate is low.  The frozen valve showed no signs of growth of any sort.  Over the last 8 years, I've had to replace two othe frozen ones and have had several more become sticky enough to replace.  The 3/4 and up sizes are fine.  It's the little half inchers that freeze up.

In answer to the other question asked.  The oil will float on the water and then will push the water down as the oil column weight becomes high enough.  That's what might make this trick work. 

Frozen or sticky stopcocks are one of the the bigger nuisance headaches I've had with Gorbash.  One threatened to foul up a 6 week cruise until I jsut decided to replace it at anchor.  No real problem and we do it regularly now:  unscrew valve, tap in wood plug, clean off old teflon tape, put on new tape, pull plug, slide finger over hole, slide valve on and screw on.

[Ron Hill]

Gary and Randy : The part about Maintenance is correct - don't try and take them apart!!  I've found they need lube!!
The vegetable oil lubing I've seen a number of times and guess that it works. 
I've just always used the waterproof/water resistant grease and have never had a problem.  I did have one that was harder to turn than the others.  I removed it one winter and put it on my work bench.  Every time I walked past it I exercised it 2 or 3 times.  By spring it was nice and limber.
When we're in the water I "exercise" the thru hulls, not just turn them on and off.