Cooling Water Problem

[Dave 71]

I lost cooling water flow whilst reversing out of my berth last week. It was fine initially, we had the boat at idle for about 5 minutes whilst slips were set and we waited for another boat next to us to leave first and give us more room. Noticed that the cooling water had stopped about 3 boat lengths from the berth. Went back in expecting a quick fix....

.....Checked the strainer and it was pretty mucky, so cleaned that out, then checked the impellor, which was fine, but sheared the head off of one of the screws fitting the plate back on. Had to take the pump off to remove the shaft of the screw and then wait for a suitable screw to arrive in the post.

I've put the final screw in today and replaced the face plate, but still no flow. After starting the engine, and getting no water out of the exhaust, there was a small amount of water in the pipe after the pump, but none in the pump or intake pipe from the strainer, seemed to have pulled a small amount of water through then nothing

I've blown air back through the strainer and out the sail drive, put a new face plate on but nothing. I'm confident that the pump is OK, I could see the belt and pulley wheel turning and the impellor rotated when I turned the wheel by hand whilst it was off. The old impellor was fine so the heat exchanger isn't blocked with bits of old impellor. What else might prevent flow?

It's a Yanmar 3YM20 engine.

 

[NormanS]

Try pouring water into the strainer to prime the pump.

 

[Kwik Decision]

As NormanS says, you often have to prime these to get them going. If the strainer is above the water line, close the seacock, remove the strainer lid, and fill with water - you could well see bubbles of air coming back up into the strainer as you do this. Then replace the lid and tighten before opening the seacock.

On ours, (3YM30, so I assume similar to yours) the strainer is below the water line, and I prime it by loosening the screws holding the pump cover plate in place, and allowing air / water to be expelled before tightening the screws back up. This is done with the seacock open. I have to do this every time the boat drys out, and so I suspect the pump needs some love, although it has a new cover plate and impeller.

 

[Kwik Decision]

Deleted - repeat posting

 

[Tomaret]

I lost cooling water flow whilst reversing out of my berth last week. It was fine initially, we had the boat at idle for about 5 minutes whilst slips were set and we waited for another boat next to us to leave first and give us more room. Noticed that the cooling water had stopped about 3 boat lengths from the berth. Went back in expecting a quick fix....

.....Checked the strainer and it was pretty mucky, so cleaned that out, then checked the impellor, which was fine, but sheared the head off of one of the screws fitting the plate back on. Had to take the pump off to remove the shaft of the screw and then wait for a suitable screw to arrive in the post.

I've put the final screw in today and replaced the face plate, but still no flow. After starting the engine, and getting no water out of the exhaust, there was a small amount of water in the pipe after the pump, but none in the pump or intake pipe from the strainer, seemed to have pulled a small amount of water through then nothing

I've blown air back through the strainer and out the sail drive, put a new face plate on but nothing. I'm confident that the pump is OK, I could see the belt and pulley wheel turning and the impellor rotated when I turned the wheel by hand whilst it was off. The old impellor was fine so the heat exchanger isn't blocked with bits of old impellor. What else might prevent flow?

It's a Yanmar 3YM20 engine.

I suffered a lack of cooling water earlier in the season. I think that the cause was an imperfect seal on the water strainer. I cleaned the o-ring and thread and tightened all the jubilee clips and for now, at least, the problem has disappeared. I also checked the impeller but that was fine.

 

[Graham376]

I suffered a lack of cooling water earlier in the season. I think that the cause was an imperfect seal on the water strainer. I cleaned the o-ring and thread and tightened all the jubilee clips and for now, at least, the problem has disappeared. I also checked the impeller but that was fine.

The large O ring seal in Vetus strainers can be a problem, sometimes cured with greasing, other times removing and inverting it, can work.

 

[Metalicmike]

I had an impeller that looked fine but was no longer bonded to the housing, tried gluing it on but nothing worked and had to replace it, Problem solved,

 

[Dave 71]

Now working! Just needed to prime via the strainer. Kicking myself that it was something so simple.