Yanmar SD50 Valve

[Adaero]

I am having trouble shutting off the brass raw seawater valve on the saildrive when I leave the boat. One of the engines is fine but the other goes down about 1/2 way and then binds. I have tried WD40 etc but with no luck.
Didn't fancy removing it so suggestions would be appreciated.

 

[jeremyshaw]

If you mean what Yanmar call "Kingston cocks" then you have my sympathy.

It's almost certainly calcification and hard to remove. If you work at it for an hour you will probably sort it, but it will come again, and access is often not great.

I made a special tool for this by cutting a slot in a socket wrench head, which could fit over the small brass arms.

It worked well until the brass arms packed in. A new cock comes at over USD 100 as I recall.

It's basically a fairly conventional tap design, and I think the threads just get calcified up.

In the end I had them replaced, at a mechanic's suggestion, with conventional lever arm seacocks, coming off an elbow into the socket. Much simpler and more effective. Probably work out cheaper too.

If you don't want to do that then you'll have to take it off and strip it down when you are next out of the water. Though if you fancy diving down you can seal up the intakes with duct tape quite effectively, then wrapped over with a bin bag. Personally I'd leave it until the boat's on the hard, but keep a bung tied nearby!