Yanmar 3YM20/SD20 saildrive - sea cock question

Twister_Ken

Twister_Ken

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On Snowbird the raw water cooling seacock is a small tap, starboard side on the top of the saildrive unit. It takes many turns to close (20?). I 'exercised' it yesterday and found that it would turn about three times from open towards closed then jam. Judicious use of controlled violence finally got it fully closed (levering it with a small ring spanner around the handle, advancing it about a quarter turn, then backing off and doing it again), after which it opened and closed relatively easily. Applied some waterproof grease externally (have I got the last tub of Duckham's Keenol extant?), crossed my fingers and hoped the problem had gone away.

Has anyone with a similar set-up had a similar problem, and if so, did you ever find the cause?
 
Twister_Ken said:
On Snowbird the raw water cooling seacock is a small tap, starboard side on the top of the saildrive unit. It takes many turns to close (20?). I 'exercised' it yesterday and found that it would turn about three times from open towards closed then jam. Judicious use of controlled violence finally got it fully closed (levering it with a small ring spanner around the handle, advancing it about a quarter turn, then backing off and doing it again), after which it opened and closed relatively easily. Applied some waterproof grease externally (have I got the last tub of Duckham's Keenol extant?), crossed my fingers and hoped the problem had gone away.

Has anyone with a similar set-up had a similar problem, and if so, did you ever find the cause?
Click to expand...

There was a similar set-up on my Volvo md2020 (with a saildrive) when I got the boat. The previous owner said you needed to close this seacock immediately the engine was stopped, i.e whilst still hot. I had it changed for a seacock (ball valve?) with a 1/4 turn between open & closed. Far easier way to shut off a seacock.
 
Identical problem with the sea cock, used to be able to turn freely but appears to have exactly the same symptoms and havent been able to free it to be able to close fully.
Havent used the, or otherwise violence . . . yet but WD wasnt helpful. be interested in solution?
 
As suggeted a ball valve may well be a bettr chice than a gate valve.


Regarding Duckhams Keenol ....... Ramonol white grease is sold as the replacement

830285.jpg
 
Repalced my Yanmar stopcock after it failed - poor design IMHO. The job was a breeze and inlet can be shut of in seconds and everything is 316Stainless.
I got the bits from ASAP supplies (no connection) see details below. All you need is an adjustable spanner and soem ptfe tape to seal the threads
best regards
Martin

Item 1 Quantity SubTotal
BALL VALVE SS 1/2"BSPFM LEVERHANDLE 1 £10.21
Part Number: 405753
Retail: £14.89. Discount Price: £10.21
Item 2 Quantity SubTotal
HOSETAIL SS316 90DEG 1/2BSPM-20mmHO 1 £2.34
Part Number: 422338
Retail: £3.41. Discount Price: £2.34
Item 3 Quantity SubTotal
NIPPLE SS316 1/2"BSP EQUAL MALE HEX 1 £1.42
Part Number: 423603
Retail: £2.07. Discount Price: £1.42

Prices may be out of date
 
I've just replaced the gate valve on my SD20's with 316 stainless ball valves. I was thinking of going to the reinforced plastic ones but they take up too much room.

IMO the Yanmar gate valves are a disgrace. Mine failed by the gate corroding so that it wouldn't shut off properly .... any I never knew whether it was fully open or not. Also the 90 deg fitting is great for fouling.

Be careful not to fit BRASS fittings. Bronze is okay.
 
Halo said:
Repalced my Yanmar stopcock after it failed - poor design IMHO. The job was a breeze and inlet can be shut of in seconds and everything is 316Stainless.
I got the bits from ASAP supplies (no connection) see details below. All you need is an adjustable spanner and soem ptfe tape to seal the threads
best regards
Martin

Item 1 Quantity SubTotal
BALL VALVE SS 1/2"BSPFM LEVERHANDLE 1 £10.21
Part Number: 405753
Retail: £14.89. Discount Price: £10.21
Item 2 Quantity SubTotal
HOSETAIL SS316 90DEG 1/2BSPM-20mmHO 1 £2.34
Part Number: 422338
Retail: £3.41. Discount Price: £2.34
Item 3 Quantity SubTotal
NIPPLE SS316 1/2"BSP EQUAL MALE HEX 1 £1.42
Part Number: 423603
Retail: £2.07. Discount Price: £1.42

Prices may be out of date
Click to expand...

I'm surprised to hear that imperial sizes worked, but take your word for it.

Sounds like a project for next winter.
 
Twister_Ken said:
Has anyone with a similar set-up had a similar problem, and if so, did you ever find the cause?
Click to expand...

It is a standard fit for yanmars using SD20 saildrives. It is also a standard problem!!! Small hole, gate valve and sea life - who would have thought it might be a problem!

I had 2 x 3GM30 engines with these. One had been modified so that a ball valve was used from the leg. The other was original and restricted water flow far too much. I had vetus strainers, and needed to be able to cut of the flow completely in order to prime these strainers after drying out. This set up is a recipe for problems.

I have just fitted new 2 x 3YM30 and have isolated the leg attachment. My engines now have their own thru-hull and ball valve for the cooling water .
 
You have to open and close the valve before and after each trip ie regular use. This was the advice given years ago on the Marine Power website when it had a forum.

I also put a smear of silicon grease on the outside of the brass valve about every 6 months. Mine has worked fine since 2004.
 
wizard said:
You have to open and close the valve before and after each trip ie regular use. This was the advice given years ago on the Marine Power website when it had a forum.

I also put a smear of silicon grease on the outside of the brass valve about every 6 months. Mine has worked fine since 2004.
Click to expand...

For now, that's the plot. Doesn't seem to be mentioned anywhere obvious in Yanmar's owner's manual, though. I might ponder whether there's a better solution when she's next scheduled to be out of the water.
 
SS seems dangerous.....

Tranona said:
Yes. The threads where it goes into the aluminium housing could be a problem. My Volvo has a DZR ball valve (I think!). Don't seem to cause any problems.
Click to expand...

Have the same issue for 6 years. Have replaced both (have a cat) SD seacocks every 2 years, and about after 18 months they seize. This last set I opened and closed every week, and oiled, and they have still seized as of about 2 months ago. When I say seize, they will not turn their full 10 rotations, only about 8-8.5 now.

Also want to replace them with a ball valve and found this thread.

Using SS would make be VERY nervous on an aluminum SD. Surprised someone went that route.

I assume the original are bronze? Can anyone confirm that?

If so, would it not make more sense to use bronze components to avoid the SD from decaying?

Want to order all the bits for this, but do not want to use SS on them.
 
kiltym said:
Have the same issue for 6 years. Have replaced both (have a cat) SD seacocks every 2 years, and about after 18 months they seize. ....
Click to expand...

Or you can do what I have done.

Seal off the SD drive inlet and fit a proper 3/4" thruhull with ball valve. This will enable a much better flow of water for cooling.
 
Talbot said:
Or you can do what I have done.

Seal off the SD drive inlet and fit a proper 3/4" thruhull with ball valve. This will enable a much better flow of water for cooling.
Click to expand...

Do the SD's not need water being drawn through them for their own cooling?
 
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