Changing Impeller on Yanmar 2GM20

[capricorn]

Will be changing the impeller on my Yanmar 2GM20 for the first time in the next few weeks.

Do I need one of these impeller extractors I see in the chandlers for 50 quid or so or can I do it with a pair of long nose pliers if I'm careful.

Any other tips for changing an impeller gratefully received !

 

[snowleopard]

if you're replacing the old one you should be throwing it away so it doesn't matter if you damage it, so long as you don't scratch the bore of the pump. i use a narrow-nosed mole wrench. in fact it doesn't seem to harm the impeller but i wouldn't want to guarantee it.

 

[branko]

It is 10 min job.You need only long nose pliers, impeller and paper gasket (if you have not , you can do it on sea from any peace of paper).
If you can be even more sure buy completely pump and you can change it for 2 min by unscrewing 2 long bolts and take away belt.It is not expencive.
Clever thing is having on board 2 spare fuel injectors also as it is second failure which can happen on sea commonlly.

 

[fireball]

We changed ours ... after spending 4 hours putting the old one in and out - didn't look like there was anything wrong with it, but it just wouldn't suck up the water. As soon as we put a new impellor in there it was straight forward. The easiest way is (as already mentioned) to remove the whole pump housing and do the rest away from the engine.

Our 4 hours wasn't wasted - we're now practised - so can change it in 10 minutes - will be handy in a big sea when the impellor next fails!

 

[Colvic Watson]

Isn't there some company that makes speed seals for the impeller housing on the GM range? I've got the 1GM with the old style nuts and bolts and wouldn't mind changing it.

 

[fireball]

Yes there is ... a friend who has a 1GM was intending to change over - I can find out details when I next see him.

 

[snowleopard]

if you have the raw water cooled engine you don't need a gasket, there is an O-ring set into the face of the pump - it shouldn't need replacing.

i have speedseals but after fitting them decided it was a bit pointless as i have to get the toolkit out to unbolt the pump anyway. i also had a lot of trouble with the pumps not sucking which was down to the speedseals - firstly finger pressure on the thumbscrews wasn't enough to compress the thick O-ring fully so the plate wasn't bedded down properly, also the impellers had worn deep grooves in the cover so water was escaping round the sides of the impeller vanes.

 

[Piers]

When putting it back in, use plenty of Silicon grease on the spindle as well as the inside of the housing. This eases the impeller onto the spindle, and gives it initial lubrication as it spins before the water is sucked up.

 

[paulrossall]

Snowleopard
I have a 2GM20 raw water cooled, fitted new in 1994. It definately does have a paper gasket and does not have a rubber seal as you have described. Maybe later pumps were different. My pump had worn a grove in the back plate as you have described, after 900 hours use, and I had it skimmed flat at a cost of "a drink" ....I gave £3. I would not have a speedseal backplate as I would be concerned about tightening up the joint enough. The pumps do not work well at low revs if there is any wear on the backplate. I calculated that they spin round at about 3 X the engine revs which would mean they go at about 10,000 RPM when the engine is at full revs. Paul