No engine cooling water

Possible. Take the hose off the inlet and open it. Be ready to close it quickly as water should spurt out!
 
They do get blocked but you should be getting something through even if it is only a trickle.
Can you push a rod down or back blast it with a hose?
The stop cock may look as if it is open but is it?
 
Had a similar problem earlier this year when we relaunced a friends Bav 36. With the engine running take the top off the water strainer and pour a bottle of water in, get the top back on quickly, this effectively primes the water system and with any luck you will see a steady flow from the exhaust.
 
Sounds like the leg is blocked to me, hose off, attach foot pump, blast backwards with air. Hopefully job done. (make sure shut off cock works easily before starting!)

Yoda
 
Knowing what you have done and might have done, could you replace the syphon bend? A friend had a similar problem and after stripping the sea water supply, pump etc, and finding nothing wrong, we short-circuited the syphon and all worked. No idea why ....
 
You mention only a dribble of water at the water pump when the cover is removed... Is the water pump really below sea level? If not then you would not expect any to dribble out anyway..

Regarding the impellor - How are you sure it's good? It might have all the fins.. and be quite new... but if sitting for 3 months, one of the fins could have become stiff and sticks in it's bent position.. I had it once and by turning the engine by hand with pump cover removed realised it would have lost suction each time this fin rotated past the inlet.

The rubber could also be rotating on the metal center insert (although unlikely).
 
Twister_Ken said:
All the normal gubbins seems to be integral with the sail drive legs, so the wire coathanger trick is a bit redundant. Reluctant to take the hose off, but I was only getting a dribble of seawater when the cover was off the waterpump and the seacock open.
Click to expand...
Assume you have the usual setup of pipe to strainer then down to pump. Try priming the filter as Galadriel suggests. Turn the seacock off, fill the strainer, put the cap on, start the engine and open the seacock. Should then suck water in. If it does not pump then it could be saildrive blocked, but it is unusual.
 
One other possibility:

Talked to service engineer today while he was giving my 3YM20 and SD20 the annual once over today. Asked about any known problems on water pumps. His view was that the inner bore wears to the point of minimal/no waterflow from about 500 engine hours (in fairly silty waters of Poole harbour). Depending on run hours / sediment load in water could be yours has reached this point. Apparently only a couple of thou wear is needed...... :-(
 
Had the exact same thing happen to me on Friday morning when I relaunched. Happy ending though (and a wonderful weekend of sailing - but that's another story!). Engine only has 200 hours (so I'm thinking too young for pump worn out) and new impeller (a possibility for failure but not the first suspect). I phoned Gary over at Yanmar agent Purbeck Marine for advice. He said:
1. Close the intake seacock
2. Pour water into the seawater strainer to fill it - making sure to fill the intake pipe too
3. Start the engine with some throttle
4. open seacock as soon as engine fires
It worked.
The system needed repriming. Must mean the pump is les efficient than it used to be though. She's been lifted5 times and always reprimed herself unaided.
Worth knowing though
 
John_Silver said:
One other possibility:

Talked to service engineer today while he was giving my 3YM20 and SD20 the annual once over today. Asked about any known problems on water pumps. His view was that the inner bore wears to the point of minimal/no waterflow from about 500 engine hours (in fairly silty waters of Poole harbour). Depending on run hours / sediment load in water could be yours has reached this point. Apparently only a couple of thou wear is needed...... :-(
Click to expand...

I know another Yanmar engineer who thinks that although the engines are very good, the water pumps fitted are rubbish. I'd first suspect a Vetus-type strainer not sealing though - I've had this happen.
 
I had the same, in my case the oil heat exchanger bit, which has small capillaries and located before the impeller in my case, was salted up. had to open it and use screwdriver to push through dry salt. i actually got some engine guru to do this, beforehand a dozen boaty neighbours had all scratched their heads over this mystery..
 
michael_w said:
Leg blocked. Bypass the problem by fitting a new skin fitting and strainer.
Click to expand...

Agreed. Thoroughly recommend it. This is what I did. I had multiple issues with cooling water flow and I decided it was impossible to keep the saildrive leg inlet 100% clear all the time. Even when working 'ok' I was never happy with the volume of water exiting my exhaust and it always seemed to be steaming hot.

Since bypassing the saildrive leg and installing a standard skin fitting I have greatly increased the water flow through the exhaust - it now comes out in healthy big glugs rather than a hissing spray and is nicely wamr but not hot. Not had any problems since.
 
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