Folks,
Don't make the impeller replacement all that complicated. If you put it in and start the engine and she pumps water out the exhaust, you've done it correctly. Though it is good practice to get the blades rotated in the right way, it is not absolutely necessary. They will flip over on the first revolution of the engine.
It is very important that an owner replace the impeller at least once, on the hard, with no pressure to, "get it done". That way when it does fail underway it will not be a panic situation. Some/many engines, not just Yanmars, have the pump in such a position that the impeller is hard to remove, even a puller won't work. In those cases it usually works best to remove the pump and do it off the engine.
Cheers,
Peter
