Re: Yanmar 3YM20 New Raw Water Pump Install Questions
With the pulley on the pump, mine turns easy when all is rebuilt. I keep a spare rebuilt pump on board and spare impeller. My number 1 cause for engine issues. My Sherwood pump will work in both rotations, cover is marked so. But as "overboard" mentioned, be careful not to rotate one way then the other. You could damage impeller. I just rebuilt my backup pump after sitting for three years and found the the impeller, although intact, the fins were bent over at the cam spot and do not want to release that shape. I am sure with some use it will straighten out, but I opted to keep that impeller as spare. I rebuilt the pump but did not install the new impeller. I will install the impeller when pump is needed. Easy to do. I might be another few years before I need it.
You say the new pump won't turn? How long has it been sitting since it was manufactured? Are you trying to turn it with the pulley on? I don't think you will be able to turn it with only the shaft.