Yanmar 3YM20/SD20 saildrive - sea cock question

No. The water only comes in through the leg for convenience - to avoid having another hole in the hull. However there are pros and cons of this arrangement and some people prefer to have a separate water supply. Accessibility to the cock on the leg can also sometimes be a problem and a separate supply can be positioned in a more convenient place, for example directly below a water strainer.
 
So, assuming one wants to replace the valves, not put new through-hulls into the boat, what is the best material to use for the nipple that screws into the SD?

It would seem the Yanmar parts are bronze, but maybe an alloy?

Looking around, bronze does not seem much better than SS. Someone mentioned DZR brass, which I am not familiar with? Obviously normal brass is not a good choice.

What about just using aluminium nipple/valves?
 
Also interested if anyone found a brass, or other solution for a replacement ball valve other than stainless , for the SD20 sea cock replacement.
 
farmer.leo said:
Also interested if anyone found a brass, or other solution for a replacement ball valve other than stainless , for the SD20 sea cock replacement.
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Nobody in their right mind would use a brass ball valve, unless they wanted to sink theirvessel.

I re-engine my cat last year with 3YM30s. I sealed of the SD20 inlets, and fitted new marelon thru-hulls.
 
prv said:
Is the "tap" (sounds like a gate valve) a built-in part of the saildrive, or is it screwed into it? If the latter, the obvious solution is to unscrew it (with the boat out of the water!) and fit a ball valve instead.

Pete
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I am waiting for someone to come back to me on this as he had a similar problem and from the bits he
showed me they seemed to be minus a gate! His description suggested the gate body recess was actually machined
in the top of the sail drive and the valve cover spindle and gate are inserted and screwed up. The water exits from a
port in the side of the Sail Drive Maybe someone can in fact confirm this is what should be there. It sounds like the
Volvo and Yanmar sail drives are similar. I will find out more tomorrow when at the marina.


My concern was that a stiff gate might get stuck in the saildrive body having torn the collar off the bottom of
the spindle! Certainly removing the gate and plugging off the top with the spindle and body and fitting a ball
valve to the water outlet would be a way to go but make sure the gate is not left behind possibly blocking the
passage.

These things need regular operation but not situated in the best place.
 
Bilgediver said:
...............................My concern was that a stiff gate might get stuck in the saildrive body having torn the collar off the bottom of
the spindle! Certainly removing the gate and plugging off the top with the spindle and body and fitting a ball
valve to the water outlet would be a way to go but make sure the gate is not left behind possibly blocking the
passage..........
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On one of my previous 3GM30. the valve would not shut properly - probably due to shell blockage. As I have water strainers as well, the real problem happened after drying out. The strainer emptied , and because I could not shut the valve fully, I was unable to top up the strainer once I was floating again. I suspect that the inlet inside the leg was also badly blocked by dead crustacean, and as a result of these two events, the engine could not draw enough water and overheated. The gate valve is much smaller than a standard 3/4" thruhull, and thus puts a fair strain on the sea water pump to supply the cooling water. I is very noticeable that there is far more water coming out of the 3YM30 exhausts than was being blown from the 3GM30 exhausts.

I would not consider using these valves in the SD20 under any circumstances. Block them off and fit thruhulls where they are easier to access.
 
Talbot said:
Nobody in their right mind would use a brass ball valve, unless they wanted to sink theirvessel.

I re-engine my cat last year with 3YM30s. I sealed of the SD20 inlets, and fitted new marelon thru-hulls.
Click to expand...

I would recommend using DZR Brass if you choose to replace the gate valves instead of a new thru-hull.

There is more info on this thread:

http://www.cruisersforum.com/forums/f54/yanmar-sd20-kingston-seacock-raw-water-valves-106818.html

The parts I ordered are in post # 24

Mark
 
kiltym said:
I would recommend using DZR Brass if you choose to replace the gate valves ............
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I recognise that DZRB is a brass alloy, but has better sea water applicability than brass, but not as good as bronze.

However, you are connecting this to aluminium, have you done any research on the effect of these two metals connected together in a salt water environment?
 
Talbot said:
I recognise that DZRB is a brass alloy, but has better sea water applicability than brass, but not as good as bronze.

However, you are connecting this to aluminium, have you done any research on the effect of these two metals connected together in a salt water environment?
Click to expand...

What material plug did you use to seal off the inlet hole in your saildrives?
 
Talbot said:
I recognise that DZRB is a brass alloy, but has better sea water applicability than brass, but not as good as bronze.

However, you are connecting this to aluminium, have you done any research on the effect of these two metals connected together in a salt water environment?
Click to expand...

I have been told the original gate vales are brass. I had them installed (and replaced many times as they became unusable) with teflon tape, and have had no corrosion that I can see in the 15 years of the boat (I have owned it for 7).

With the DZR Brass, I used a good quality pipe dope to insulate the metals, based on what others have done.

Some installers recommended using Lanacote, but I felt a good pipe dope would do the same (probably better since Lanacote isn't really a thread sealer). I used Loctite 565 (or 567).
 
Surprised to see this thread re-surface after all this time!

FWIW, after greasing (Keenol) the thread of the seacock, it has since open and closed like a well greased seacock should. No complaints, but maybe Yanmar or the installer should have greased it, rather than waiting for the owner to sort it out.
 
Am I correct in thinking that Bronze fittings will be OK into the aluminium sail drive or would DZR or SS be better?
 
blxm said:
Am I correct in thinking that Bronze fittings will be OK into the aluminium sail drive or would DZR or SS be better?
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I'd avoid direct contact between aluminum and bronze, brass or stainless steel!
 
VicS said:
I'd avoid direct contact between aluminum and bronze, brass or stainless steel!
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I guess that the Yanmar original is bronze but I would use some grease I was fitting a new valve. I'm not sure whether that's classed as direct contact or not but unless one can find an aluminium or "plastic" valve it's probably the best one can do I suppose.

Richard
 
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