raw water impeller

[fiestaMojo]

I have a yanmar 2GM20F on my boat. I want to pull the raw water impeller, is there a trick to this? The access cover faces aft toward the block and it seems a little tight. . .
also, can I flush the raw water system without running the engine?

 

[Dan Johnson]

Fiesta..

The 2GM and 3GM have what appears to be the same raw water pump mounting plate. On my 3GM I first close the raw water intake valve, then unbolt the pump mounting plate, loosen the hose clamps and rotate the pump so that the back is facing you.

Taking off the backing plate then becomes relatively easier. On mine, I replaced the Phillips head screws with 4mm bolts to make it less likely to strip out a screw head trying to remove it.

You can't flush the raw water system without running the engine. Between the raw water intake strainer and the pump I have a hose connection and ball valve assembly that permits me to couple a five gallon water bucket to it and fill it with anti-freeze to winterize it. With the raw water intake valve closed, the engine is run briefly to draw in about 2 gallons worth. Fresh water could also be used to flush out the raw water system.

You could possibly hook a shore water hose to this arrangement to flush it out, but I don't know if you would want to risk filling up the water lift muffler and anti-siphon loop and have it back up into the engine through an open exhaust valve. Better to run the engine.

 

[sailaway78]

Impeller

It is necessary to pull the pump to change the impeller on these engines. Pretty easy, as you can pull the two bolts on the mounting bracket, and you have the pump in your hands. Maybe it's possible to do it without pulling the pump off, but would be a real PITA. As a side note. The Yanmar impellers have been known to spin the hubs. I had this happen last year on one with about ten hours on it. Johnson makes the same impeller, except the pin on the Johnson goes completely through the rubber, instead of just the hub as the Yanmar does. I would highly recommend you not use the Yanmar impeller.

 

[fiestaMojo]

You can't flush the raw water system without running the engine. Between the raw water intake strainer and the pump I have a hose connection and ball valve assembly that permits me to couple a five gallon water bucket to it and fill it with anti-freeze to winterize it. With the raw water intake valve closed, the engine is run briefly to draw in about 2 gallons worth. Fresh water could also be used to flush out the raw water system.

You could possibly hook a shore water hose to this arrangement to flush it out, but I don't know if you would want to risk filling up the water lift muffler and anti-siphon loop and have it back up into the engine through an open exhaust valve. Better to run the engine.[/quote]

the boat is out of the water. . . I planned to just drain the raw water system and pull the impeller. . .

 

[DougM]

There are 2 versions of the water pump on the 2GM20f. The one that I have is the "euro" version of the engine and it has a Johnson pump on it. The "Japanese" version has a pump the is somewhat different in that it has a different impeller and the cover has a gasket. My engine has the same pump as some westerbeke engines. Its backing plate has an "o" ring seal and an impeller wit a cross bolt rather than a keyway. In any case, the easiest way to change the impeller is to pull the pump completely off the engine and do it in the open, you will save yourself a lot of time compared to doing it while still attached to the engine.

 

[Blitz]

Would a Speed Seal help?

It is necessary to pull the pump to change the impeller on these engines. Pretty easy, as you can pull the two bolts on the mounting bracket, and you have the pump in your hands. Maybe it's possible to do it without pulling the pump off, but would be a real PITA. As a side note. The Yanmar impellers have been known to spin the hubs. I had this happen last year on one with about ten hours on it. Johnson makes the same impeller, except the pin on the Johnson goes completely through the rubber, instead of just the hub as the Yanmar does. I would highly recommend you not use the Yanmar impeller.

Nice N Easy - I believe you have a Raw Water 3GM - do you have the Johnson Part number?

Also, has anyone tried the Speed Seal to help out, and can it be done without removing the entire pump with the Speed Seal since you don't need to be as careful as with the the paper yanmar gasket?

 

[Warren Milberg]

Hard for me to imagine the Speed Seal would be much of an improvement in impeller changes for the rearward-facing water pumps on these engines. Even when I pull the pump off the engine to get the cover off and the old impeller out, I need to use a needle nose pliers to pull the old impeller out -- and it always fights me. And getting the new impeller in also requires two hands to squeeze the blades down and wiggle/ push it onto the shaft. Can't imagine doing this with the pump in place and facing aft.

 

[chuckwayne]

I've had a speedseal on both my Yanmars (2gm and 3gm) and it's a great help-you still have to pull the pump off the engine but it's safe, easy and fast-remove 2 large thumbscrews and loosen 2 instead of 6 tiny screws-no tools-and the plate slides off. after you swap the impeller the plate slides on and is held by the 2 loose screws until you put in the 2 you removed. I tie a piece of small stuff around the impeller to compress the blades and the new one just slides in.

 

[Steve Dion]

The speed seals do help. You loosen all four thumb screws and remove two of them. R/R the impeller and you are almost done. You may need to replace the gasket of yours does not have an o-ring.

Those little screws are buggers and were never a good idea.

Then if you try to replace the impeller on the JH motor the less you have to mess with bolts the better off you are.