Yanmar 1GM10 not pumping water

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smth448

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Just as we were returning to the mooring after our last sail of the season last week the engine decided to stop pumping water.
We lifted out a couple of days later but before doing that I tried to find out why. Checked the filter, empty. Checked the pipes from seacock to water pump, clear. Opened the seacock, water came in. Changed the impeller as the old one had become detached from the bronze centre. Still no luck.
I guess the impeller got ruined from running dry.
I had a problem on another engine a few years back where the water pump stopped puming because the water filter was cracked and letting air into the system. Could it be this or could there be a blockage in the engine? The impeller was all there so I don't think any bits of it have come off and gone into the engine.
This was a sudden failure not a gradual decline.
Anybody out there with any ideas?
 
There have been reported failures of the impeller rubber to shaft joint over the years. My understanding was that this was an isolated batch of impellers, possibly not Yanmar's own, that were faulty. I haven't read of the problem for a while - was this an old impeller? Remedy seems to be to buy only the Yanmar product.
 
New, genuine Yanmar impeller installed at the beginning of 2007. When changed to a spare it still didnt work.
 
Sorry, didn't read your original post well enough. Is the drive pulley still connected to the shaft and does it all turn as it should?

We have problems sometimes after sailing in lively conditions. The pump loses suction when the inlet comes out of the water and then doesn't re-prime when the engine starts. Even putting a check valve immediately after the seacock has not fixed it entirely. We occasionally have to top up the suction strainer with water to restore flow.
 
I had problems with water flow. I cannot remember the the symptons only the solution. I removed the thermostat housing, took out the thermostat then poked into the pipe with a screwdriver. After a little gentle prodding something gave way and water started running out of the hole. Seems it was crusted up with salt. Might be worth a try.
A good run through with fresh water should help as well.
 
Check the rubber hose going vertically up from the pump to the thermostat - it often becomes blocked.
The impeller problem is ongoing - admittedly it used to be worse, but there are still problems. You could try a Globe impeller. Unfortunately ASAP don't sell them anymore, but the enquiry I submitted to Bainbridge Marine was answered by this:
"The impellor for the Yanmar 1GM is Globe model 321, you can order this from any UK chandler using the Bainbridge Marine part number Q133009. RRP £13.60."
 
Yanmar

never made the impellers or the pumps - they're all made by Johnson.

On their more recent engines they've given up the pretence and the pumps are all badged as Johnson.

There are 3 types of material used on the impellers neoprene, nitrile and i69. Put the wrong material in and the impeller life will be short (and brutish).

From the sound of things the pump is sucking air - could be internal (scoring on shoe or rear/face of pump), inlet from the top of the filter body (try smearing the O-ring with a little silicone grease).

When you fit an impeller lubricate it with either glycerine or saliva, and mahe sure the vanes are trailing the direction of rotation.
 
Re: Yanmar

The 1GM has a different pump from the 2 and 3 cylinder engines. As far as I know the impeller problem has gone away. I have used both Yanmar and Globe without failure.

The two most obvious causes of not pumping are the short vertical rubber hose up to the thermostat housing. This blocks up and may actually be a contributory factor to the failure (unable to pump the water up). And the other, if you have a Vetus type filter above the engine and you have either cross threaded the top (easy to do and it feels if it has seated onto the O ring) or there is a crack in the top letting air in. You can check that the pump is pumping, after cleaning the pipe, by closing the seacock and filling the filter body with water from a hose or watering can. Once it is pumping open the seacock and put the top back on (if it is not cracked).

I also once had a problem of air getting in because the jubilee clip on the inlet pipe to the filter had stripped its thread and appeared to be tight but wasn't so let air in. So worth checking all the clips.
 
Re: Yanmar

Two possibilities:

1/ the pressed steel water pump pulley has been known to become loose on its spindle and even to wear the drive hole round so not turning the pump
2/ eventually, wear to the front plate, back surface and the little replaceable built in hump will cause the pump to fail to prime and you end up having to top up at the filter to get it going. the pump can be re-conditioned (replace front plate and hump, machine face.) but I found it easier to buy a new pump.
 
Re: Yanmar

Sorry, not relevant to the 1GM. The water pump is driven from the oil pump drive shaft, not by a belt and pulley.
 
Thanks to you all for the advice. I will try all of these at the weekend.
I don't think the pump is worn out as it was replaced at the beginning of last season. I will check for air leaks and the pipe on from the pump.
 
While at it, check all the piping. I had similar situation this summer, spent 11 hours searching the cause - checked the water filter, replaced impeller, took out the thermostat, poked every piece of pipe, than did everything again - all in wain, and SWMBO on board, VERY unhappy. Next morning, after being towed to marina, mechanics did all the same things as I did, except they checked one little peace of pipe attached to the engine. Voila - two broken wings of an impeller replaced god knows how many years ago got stuck there and blocked water flow from that point onwards. They did it in less than 1 hour!!! Turned into a very pleasant cruise after this.
 
just a thought........I've got a 1GM10 and it has a manual starting handle - why not take the front off the impellor chamber and turn the engine over by hand....at least you'll see if the impellor goes round.....if it does that cuts out all the suggestions of a mechanical drive failure
 
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two broken wings of an impeller replaced god knows how many years ago got stuck there and blocke

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i can never understand why marine engines dont have a strainer fitted between the pump and the engine.It would save a lot of work looking for the impellor bits.
 
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