Thru-hull valves ( “Seacocks” ) - the Achilles Heal

[K2MSmith]

Since there has been much to do about boat sinkings and bilge floodings, I thought it might be worthwhile for me to become familiar with all of my thru-hull fittings in my still relatively new to me 33. The speed and depth sensors I regularly check and have replaced o-rings on the former . ( with boat in water ). I think I have located all of the other thru-hulls but I’m tempted to don gear and dive the boat to see for myself. Most of my seacocks are made of some kind of plastic or composite . So I gather they are not ( original? ) . The seawater intake for the head looks like bronze . To be honest , I’m a little nervous about fussing with them until the next haulout since I know valves tend to leak if not exercised and I don’t have any history on this other than I did shutoff the seawater input for the motor when I replaced the water pump impeller. It doesn’t leak . I’ve started to do this one at a time with the other valves . ( open / close ) and recheck after a few hours for leaks and recheck again . ( having mild OCD has its advantages but it can haunt you ) .
Any suggestions on recommended maintenance? If I don’t know the history of the valves , should I just start replacing at next haulout ? ( in 1-2 years ) . If these valves leak after turning , is it usually a drip ? It would seem to me that is it better to keep the valves exercised and turn them every few months , than to let them sit (?) .

 

[p.gazibara]

If they are the composite variety, they will likely last half a century and require little if any maintenance.

They early ones sometimes got a little stiff if the plastic swelled. You may need to lightly tap the valve handle with a hammer to get it to move. Once moving, it should be fine.

I would not be scared to exercise them.

-p

 

[Christian Williams]

The sinking you are probably referring to is entirely undocumented and the owner avoids explanation of any kind. His one guess, "seacock," is useless without information to support it or any account of the accident chain.

The some kind of plastic you refer to is likely Marelon, a reinforced polymer specifically designed for marine use. Marelon has a superb reputation. If your seacocks are of some unknown plastic, that warrants immediate attention. Marelon seacocks by Forespar do not need lubrication (Forespar says). They are stiff when new. They are to be exercised periodically so glop does not dry inside and make them stick.

Seacocks are not the "danger." They are necessary and proven. They do not "break" suddenly, although I suppose they might if you drop a 50-pound tool box on them (so will your GPS). Every seacock should have a simple wooden plug attached by light line for such unlikely occurance. Pound the plug in with a hammer to stop the ingress of water, which will be hard to miss.

The danger is the hoses attached to the seacocks. They are attached by two hose clamps that must be reliable. The hoses must be considered critical components and inspected and changed when questionable. A hose that falls off an open seacock will sink the boat, for which reason many owners close the seacocks when leaving the boat for peace of mind. That's all it is, because if an open seacock is likely to sink your boat at the mooring, I don't know why anyone would go sailing on the boat with the seacocks open.

 

[K2MSmith]

If they are the composite variety, they will likely last half a century and require little if any maintenance.

They early ones sometimes got a little stiff if the plastic swelled. You may need to lightly tap the valve handle with a hammer to get it to move. Once moving, it should be fine.

I would not be scared to exercise them.

-p

I have just read another article about the fiberspar valves . The PO like to use top end stuff, so I’ll try to get closeup photos of the valves to see what I actually have .

 

[K2MSmith]

, I don't know why anyone would go sailing on the boat with the seacocks open.

Thanks Christian for the info . my previous message should have said “forespar” . My hoses and clamps all -look- pretty new and shiny , but I’ll check those. Do you mean “ sescocks closed? The cockpit drains , salt water intake to engine would stay open while sailing. . Maybe you mean sink / head seacocks could close ?

 

[Christian Williams]

I was being a wiseguy. Generally folks open all the seacocks for sailing, so they can use the head and the sink and the drains and the engine. It is recommended to close most of them for safety when leaving the boat in the slip. I refuse to do that on the grounds that my open seacocks are safe at all times, and I am certain of it, and stand by it. Call it a quirk. Most people close them when leaving the boat, and why not?

 

[Filkee]

Closing the thru hulls sometimes leads to forgetting to open them again which is i suppose why it’s recommended that you check to see water coming out the back when you start up.

 

[Kenneth K]

The precursor to Forespar's Marelon valves were the original RC Marine Marelon valves. I had some of both on my boat.

After Forespar took over from RC, they redesigned the valves with a better fitting for the handle-to-ball-valve connection. The RC design had a weak point leaving the handle likely to strip/round-off, rendering the valve useless. The RC's valve handle also moved in only one direction (90 degrees rotation) while Forespar's rotate both direction (180 deg). The 90 degree rotation in the RC valves was another weak point. Once the valve handle was "up" (valve open) there was no indication of which way to turn it to close it. Many valve handles were likely broken while owners tried to rotate them the wrong way (against the built-in stop) while trying to close them.

I did a blog post about it here: https://ericsonyachts.org/ie/ubs/forespar-mf850-marelon-ball-valves.575/

 

[Geoff W.]

I would think more likely than the seacock failing after a long time would be the backing plate rotting away, given that a lot of them were marine ply with dubious water protection. Not really sure if that would lead to the seacock breaking free of the hull, but it doesn't sound like a good part to have rot away.

 

[nquigley]

Ken - That's a great blog post.
I had great ambitions of replacing all my Marelon seacocks when I hauled out for a week last September to paint (two were frozen in the open position). But, I soon realized it was going to take more time than I had, so I only replaced to the two frozen ones - I used TruDesign seacocks, screwed into the original through-hulls. Fortunately, the wooden backing pads were solid and with a good paint covering.
The remaining TruDesign seacocks are patiently awaiting my next haul-out.
I've become a very keen seacock exerciser!

 

[nquigley]

I would think more likely than the seacock failing after a long time would be the backing plate rotting away, given that a lot of them were marine ply with dubious water protection. Not really sure if that would lead to the seacock breaking free of the hull, but it doesn't sound like a good part to have rot away.

If that ever happens to mine, the TruDesign seacocks are a great solution - they come with a collar that rests directly on the hull - no backing plate needed, and fully ABYC-compliant.

 

[gabriel]

I would think more likely than the seacock failing after a long time would be the backing plate rotting away, given that a lot of them were marine ply with dubious water protection. Not really sure if that would lead to the seacock breaking free of the hull, but it doesn't sound like a good part to have rot away.

When I replaced my leaky gate valve it made me cringe when I realized that the backing plate was so rotted out it could’ve easily fallen out under way without much force leaving the whole assembly loose.

 

[Kenneth K]

While Forespar does make actual seacocks, what most of us are referring to are just ball valves attached to plastic (reinforced) through hull stems:

Since the ball valves just sit on top of the trough hull rather than having flange that attaches directly to the hull (or backing plate), all the applied bending forces act on that small plastic through hull fitting.

While Marelon ball valves can stick, and sometimes their handles can break off, that's not going to sink your boat. But, I don't think the valve body itself ever crushes, splits, or cracks open. The weak structural link is always going to be the plastic through hull fitting. A rotted backing plate would make things even worse, or could itself be the cause of leakage.

 

[Christian Williams]

I just had mine off. The ball valves were clean, but still remained pretty stiff after scrubbing with soap and water. I tried a little silicone and a dab of grease. Made no difference so I washed it off.

...

 

[G Kiba]

Service the valve with...

MareLube Lubricants

 

[Marlin Prowell]

I just had mine off. The ball valves were clean, but still remained pretty stiff after scrubbing with soap and water. I tried a little silicone and a dab of grease. Made no difference so I washed it off.

..View attachment 38723

I had someone at Fisheries Supply suggest this Trident Series 144 hose for my head intake hose. I discovered later that Trident says:

NOT RECOMMENDED FOR BELOW WATERLINE THRU-HULL CONNECTIONS.

Trident Trident VAC HD Bilge & Live Well Hose - #144 -

Heavy duty bilge, drain and live well hose. Clear vinyl (FDA) corrugated with black hard PVC helix and smooth tube. Read More →

tridentmarine.com

I replaced it.

 

[Christian Williams]

Correction to my earlier remark: the page for Forespar ball valves says yes, lubricate them. Easy to do for above-water cockpit drains, more awkward for the rest of them. I should have done this from the outside at recent haul out.

Click to enlarge.

 

[gabriel]

Correction to my earlier remark: the page for Forespar ball valves says yes, lubricate them. Easy to do for above-water cockpit drains, more awkward for the rest of them. I should have done this from the outside at recent haul out.

Click to enlarge.

View attachment 38730

I guess that’s one advantage of a bronze valve by groco, has a zerk fitting so it can easily be greased any time.

 

[Rocinante33]

Since there has been much to do about boat sinkings and bilge floodings, I thought it might be worthwhile for me to become familiar with all of my thru-hull fittings in my still relatively new to me 33. The speed and depth sensors I regularly check and have replaced o-rings on the former . ( with boat in water ). I think I have located all of the other thru-hulls but I’m tempted to don gear and dive the boat to see for myself. Most of my seacocks are made of some kind of plastic or composite . So I gather they are not ( original? ) . The seawater intake for the head looks like bronze . To be honest , I’m a little nervous about fussing with them until the next haulout since I know valves tend to leak if not exercised and I don’t have any history on this other than I did shutoff the seawater input for the motor when I replaced the water pump impeller. It doesn’t leak . I’ve started to do this one at a time with the other valves . ( open / close ) and recheck after a few hours for leaks and recheck again . ( having mild OCD has its advantages but it can haunt you ) .
Any suggestions on recommended maintenance? If I don’t know the history of the valves , should I just start replacing at next haulout ? ( in 1-2 years ) . If these valves leak after turning , is it usually a drip ? It would seem to me that is it better to keep the valves exercised and turn them every few months , than to let them sit (?) .

Kevin,

My boat (hull #24 to your #18) had all Marelon ball valves on old style Marelon thru-hulls from the factory. I had a problem with one or two freezing in the closed position after being exercised, but not often enough, and this was a know problem then, since corrected. So I had to don a wetsuit and snorkel and stick an old style toilet plunger over the outer curvature of the hull to cover that thru-hull opening. It stopped all water ingress. Then back inside to change to a new ball valve, while the wooden plug and mallet were standing by. Then back into the cold water to remove the plunger head.* All done in the water, so it made me a bit nervous but it worked well!

I could have tied a line to it or screwed a line to it with a stubby piece of handle and saved myself the second dip, and just pulled it off from above with the line!

 

[1911tex]

So I had to don a wetsuit and snorkel and stick an old style toilet plunger over the outer curvature of the hull to cover that thru-hull opening. It stopped all water ingress. Then back inside to change to a new ball valve, while the wooden plug and mallet were standing by. Then back into the cold water to remove the plunger head.* All done in the water, so it made me a bit nervous but it worked well!

I could have tied a line to it or screwed a line to it with a stubby piece of handle and saved myself the second dip, and just pulled it off from above with the line!

Keith: How did you get the toilet plunger to stick to a not so squeegee clean hull? What did you use to scrub the area for a positive plunger suction? How did you push the plunger underwater without pushing yourself away from the hull...the plunger requires a hefty push to create the suction?

I ask because I tried this also last year without any luck! I want to try this exercise again....actually I also want to use the plunger as a handhold to scrub the mossy stuff off the hull bow to stern as well.