Yanmar SD20 Kingston Seacock raw water valves

[masterov]

thanks, Wotname!

Can someone measure the diameter of their pipe, please? Mine measures ~34mm, yet Yanmar dealer assures me that the part is the same for SD31 and SD20.

Boatguy30 - people above are talking about exercising it before every start, otherwise it corrodes. I don't think doing it every oil change will be enough. I tried doing it once a month, and even that was insufficient.

[kiltym]

Originally Posted by masterov

Boatguy30 - people above are talking about exercising it before every start, otherwise it corrodes. I don't think doing it every oil change will be enough. I tried doing it once a month, and even that was insufficient.

We did it every week, and still not enough. Within 6 months it would no longer close fully. And we did this on 4 brand new seacocks over 3 years. All the same.

The parts I supplied above all worked (on SD20), and still work just as they should. No special threads involved. Installers and manufacturers should simply replace the part at installation IMO.

[masterov]

Thanks, kiltym!

Could you please measure the diameter of your pipe that is screwed into the saildrive?

Mine measures 34mm:



which doesn't correspond to 1/2in size of your parts.

[kiltym]

Originally Posted by masterov

Thanks, kiltym!
Could you please measure the diameter of your pipe that is screwed into the saildrive?

Sorry, sold the boat......

[ggray]

Can't help on specifications of these valves, but can say that I'm still using the original 18 year old valves that came on my SD20. Bought one new one as a spare, and at that price, I want to preserve my originals!

Every haulout, I remove and clean them with WD40 (through may open/close), and then lubricate with FluidFilm or some other like lube (through many open/close). And I rarely exercise the valves between haulouts, just when winterizing.

I'm mainly on the lower Chesapeake, so not "full salt".

I modified a socket to operate the valves when tight

[masterov]

I emailed Yanmar, and got the following response from them. I am surprised that the material is brass.

Hello Alexei,

I would first like to thank you for taking the time to send in your kind inquiry. Second, please excuse my delay in replying as I did not have this information on hand.

Please see information below:

The thread is R1/2-14.

This should be the same as BSP taper thread according to some Google searching.

(Material CW617N = brass).

I hope that this will answer your kind inquiry and hope you have a great day.

​Thanks
Michael Dollfuss
Customer Support Technical Rep.
Customer Support Department
Marine Engine Division
Yanmar Marine International B.V.
(Yanmar Recreational Marine of Americas)

[masterov]

Yesterday, I finally found the right size nipple, was very excited, and then lo and behold, I held it next to my saildrive, and it became painfully obvious that the size is not even close.



As I said before, the actual part in the saildrive measures 34mm, which is roughly 1 1/3 inches.

Looks like the only option for me is to put the boat on the hard, unscrew the part, and take it with me to the shops in order to find a match. (unless someone can figure it out from the photo)

[ggray]

I'm not where I can measure anything, but I can say that if the Yanmar Kingston cock is indeed 1/2 inch NPT (and that size seems right to me), the OD of that is .84 inches, smaller than what you have.

Perhaps it's not original?

It is odd that Yanmar has this special fitting. The only reason that comes to my mind is perhaps by closing off the seawater somewhat closer to the housing it is screwed into (as compared to a ball valve), perhaps it is less vulnerable to freezing/bursting when shut off for winterizing. Just a guess.

[broken pete]

Hi all, I would like to bring this thread back to life if I may?

I am also looking into replacing my seacock with 316 Stainless Steel. I have read through a lot of these threads and it seems to be the bets option, although I have to say it really scares me screwing a stainless nipples and elbows into this cast aluminium saildrive. All the PTFE tape in the world isn't going to put my mind at rest.

But then I look at the old valve, its brass (and not the strongest), its been in the saildrive for 20 years and I cant see a single scrap of corrosion on the thread or the housing.
Perhaps the anodes in the saildrive are arresting the corrosion? is this why they are surviving?

I would also like to point out that my thread is definitely 1/2" NPT and not BSP as commonly assumed. Looks like Yanmar made an American version somewhere down the line.
Thanks all

[masterov]

Here is what I did with mine:

[broken pete]

looks good, i see you chose bronze instead of stainless. Any particular reason?
cheers

[masterov]

Sometimes you just have to go with what's available at the chandlery

[a64pilot]

Originally Posted by broken pete

looks good, i see you chose bronze instead of stainless. Any particular reason?

cheers

I believe that stainless steel and aluminum have a dissimilar metals corrosion issue, of stainless is used it’s possible that over time it could corrode the aluminum threads

[Sailorman Ed]

Resurrecting this thread again, I unscrewed the Kingston valve, it had 4 threads engaged. Screwed in a 1/2" NPT and got 2.5 threads. What about retapping for NPT? BSP fitting are much more difficult to get.