Re: Merc 4.5 - Impeller stuck on shaft
Grant, that's the way to go on this. If you have an old flat-bladed screwdriver to waste, you can make a very good impeller splitting tool by sharpening the tip to a "knife-blade" edge. This very thin blade makes it easy to split the brass insert, even with the all the rubber still on.
A chisel works well but since it's wider the rubber will make it spring back, thus the suggestions to strip all the rubber away before attempting to split the insert.
Another thought, it's tempting to try and split it where the impeller key is, since it's weakest there. The only caveat about that is that you have to be careful or you can drive the impeller key into the stainless pump insert and ruin it. If the insert was bad anyway, no loss but a shame to wreck a perfectly good one.
Anyway, the splitting technique is about the only way you're gonna get that pesky ol' impeller off the shaft! Be sure to clean up the driveshaft before installing the new impeller. Any rust will bind the impeller which needs to be free to shift up and down in the pump for best operation.
Before you install the new impeller, put a dab of grease on the driveshaft flat to hold the key in place. Center the key on the flat. Make a mark (indelible marker or whatever works for you) a ways up the driveshaft and inline with the center of the flat.
Lay a thin coating of grease in the pump insert and also on the blades of the impeller.
When you install the impeller, line up its keyway groove with the temporary mark on the driveshaft. Turn both the impeller and driveshaft clockwise while pushing the impeller down into the pump body.
Then you'll see what the mark really does for you, since when you're doing this you can't see key or flat on driveshaft!
If you held your mouth right (like Granpa always said you didn't do when you weren't catching any fish!), the impeller will be seated into the key. If not, the key was pushed to the bottom of the pump and time to start over! Move the driveshaft in both directions and confirm that the impeller is being properly driven by the key. You'll know if it is.
That's about all there is to it, the rest is just reassembly.
HTH..........ed
