Yanmar water-pump priming

[JimC]

I know there have been several posts about Yanmar water pump problems so apologies if this has already been covered - I haven't found a direct reference. The sea water pump on my GM20F normally works perfectly but, if the boat has dried-out it takes about a minute and and a lot of revs before water starts coming out of the exhaust. If I just let the engine tick-over it would never self-prime, I have to rev it up and I worry about burning out the impeller which is presumably running dry during this period. The pump is the type with an 'O' ring under the cover rather than a gasket and changing the impeller makes no difference. I suppose it would help if I closed the seacock before drying out but I seldom remember.

These are supposed to do great things for water pumps, has anyone used them? http://www.kpm-marine.com/rebuildkits.html

 

[vyv_cox]

Perhaps the best way of avoiding the problem is to fit a Vetus strainer as recommended, above the water line. You will then always have a reservoir of water above the pump to prime it.

The other point is that the pump can suck air from both sides of the impeller. This means not only through the cover and its gasket but also through the shaft seal. My 3GM always suffered in this way and would not prime after sailing in a seaway for an hour or two. Since I replaced the shaft seals it has not happened in the past three or four seasons.

 

[JimC]

Thanks for that Vyv, I'll have a look at the seals on the shaft side of the impeller. Unfortunately I can't raise the level of the strainer without major modifications as it's mounted directly onto the seacock which is under the rear berth and I think above the waterline would mean above the mattress.

 

[prv]

Unfortunately I can't raise the level of the strainer without major modifications as it's mounted directly onto the seacock which is under the rear berth and I think above the waterline would mean above the mattress.

Could it move into the engine compartment? That's what I did with mine, which also had a bronze strainer on top of the seacock originally.

When I first start up after lifting in, I pour a jug-full of water down through the strainer to prime the pump. After that it manages ok, even after drying out.

Pete

 

[JimC]

Thanks Pete, I'll check but I'm not hopeful. I think my best bet is remembering to close the seacock before drying out. That should retain the full volume of water on the input side of the pump. I already have to remember to bleed the shaft seal after drying out. It would be nice just not to dry out but this is Lancashire: 10 metre Springs, everywhere dries out round here.

 

[Burnham Bob]

another vote for the vetus strainer above the water line. i always filled mine up with water from a kettle first thing in the season before opening the sea cock. that way there was a complete 'loop' of water from the inlet to the impellor. when you opened the sea cock the syphon effect kept the water in the system.