Yanmar SD20 Saildrive sea cock won't close

[Stenn]

Anyone have an understanding of the internal construction of the raw water sea cock valve on my Yanmar SD20 Saildrive...the valve feeding my raw water strainer/filter ?

How could this valve fail internally such that when it's tightened "closed," sea water still pours from the valve as if it's fully open. Turning fully clock-wise or counter-clockwise does nothing to change the flow.

...how could this be ?

Thanks for any feedback and insight.

Jeff
s/v CatNapper

[hugosalt]

Valves have a long history of being problematic. Look up threads here on CF and on other forums. Don't have time now but will revisit later.
In a nutshell... valve may seem that it closes, however it get stuck and one thinks it's closed. It is not. Think it takes a full ten turns to close. More than one of us have thought they closed valve only to find water still flowing.
I have removed mine numerous times to clean up and finally last month I could not get it to close at all. (and this is my second valve from Yanmar.
Be aware, if you decide to replace of...dissimilar metals and incompatable threads.
More to come...

[Plumbean]

Following. One of my winter "to do" list items is to ditch this valve and use a proper seacock so as to avoid having the intake getting clogged with barnacles.

[hugosalt]

No clear cut answer from me, just some history of problem as I know it.
Maybe someone has figured out a satisfactory replacement.
Valve does not close until it has 10 full turns. What happens is that after some time, months, valve does not fully close because it will stop at 6,7,8 turns so you think its closed.
I and many others have worked these valves with very little success. They work for a while then same problem.
There are threads that go back about 10 years on subject here on CF and also sailnet.
Some fixes over the years...
*Plug SD intake and go with a dedicated thru hull for RW intake.
(Probably the best answer but I don't want more holes in boat.)
*Replace with SS fittings/ball valve or DZR Brass ball valve or bronze
(all NOT GOOD as not compatible with alunimum, Although very possible that Yanmar original valve could be brass??)
Then if still considering swapping out valve,
there is a debate on proper threads
1/2" NPT? or BSP? then is it tapered or parallel threads...
and on and on.
Over the years, in reading the old threads, some say all above has been done with success although I find it very scary fitting dissimilar metals.
I will be connecting my stuck open Yanmar valve to a short sturdy hose and then a ball valve for now until a better solution comes about.

[ggray]

Every haul out (usually every other winter) I remove both valves (twin saildrives) clean and exercise repeatedly with WD40 or the like. Then lube and exercise repeatedly with Fluid Film or the like. I probably should exercise them in the water but I don't.

One valve lasted 19 years (maybe 21) and I just replaced the second at 23 years.

I have wondered if these valves are made the way they are so there won't be much water inside them when they are closed...and vulnerable to freezing??? My engines/saildrives are not inside or under the cabin where it wouldn't get as cold in the winter.

[hugosalt]

ggray, About the same experience with my valves as have owned boat from new for 38 years and my 2nd valve is at end of life. Worked valve at each haul out (annually) and sometimes while in water, but I use Tuf Gel.
Are your valves fully functioning after 2 years?
My issue is I never know when valve will not fully close.
Big concern for me as we sail all winter here in New York and when we hit a cold spell
I winterize motor and want valve closed for sure.
Although I swore I would not buy another Yanmar valve, am actually thinking I might and then backing it up with a ball valve.
Good point/theory on valve design re freezing.

[Rapanui]

The valves are a pain but can be made to close with a bit of effort. When the valve is open apply water proof grease to exposed threads. Use a small socket with short extension over the sharp handles, to save your hands, work backwards and forwards until moves easily, close a bit and repeat. Have managed to keep both of ours able to close for 12 years. Do not try excess force, just work back and forth until it loosens up.

[Tupaia]

Not being familiar with these sail drives I assume they are gate valves. These are outlawed in most industries for critical service valves. Alternatives are indicating valves such as "outside stem and yoke valves" and "globe valves". Both types are readily available and inexpensive so why not just replace them. Quarter turn globe valves would be the most obvious option.

[ggray]

Hugosalt, yes they are still operable at haul out each 2 years. And if I can't get them moving COMPLETELY freely and smoothly, I replace them. I want to feel confident that I can close them if necessary. But as I said, this didn't happen until they were each about 20 years old or more. They are rather expensive so I try to make them last as long as possible.

Tupaia, they are not gate valves. I don't have a picture, and can't find one from Yanmar, but they are compact, with a built in 90* elbow. Picture a small pipe tee with one of the side openings (but with male threads) screwed into the side of the saildrive. The opposite side is where the threaded valve screws in like a bolt to block off the water. When the "bolt" is unscrewed, it allows water to enter the tee and exposes the center of the tee allowing water to exit through the center of the tee. I hope that makes sense.

Other than the possibility that with less water inside the body when the valve is closed, they would be less likely to freeze, their compactness makes them less subject to damage. My confession: This past winter after I removed and lubed them, I lost track of them. Between the boat, the truck (or was it the car?), the cabin , and my shop, I forgot where I had stowed them. Launch time was approaching and with the supply chain, delivery of new ones (I planned to replace one anyway) was delayed; I was desperate. As a backup, I cobbled together parts as you suggest, but I was concerned about how long the lever arm had become. Then I found the old ones, and the new ones arrived to give me one spare.

I think this valve is a reasonable solution. Just keep it lubed.

[Sailorman Ed]

I replaced them with SS ball valves and a thread adapters ( I forget now if it was a metric to NPT thread) but the end result was sooooo much better. I could be sure it was closed and a quarter turn ball valve was much easier than trying to reach down and turn the Yanmar valve. Oh, and much cheaper. I think I got everything from McMaster.