Had a really tough impeller on a V-drive that wouldn’t budge. Last time I changed it was probably 3-4 years ago, this boat doesn’t get used but maybe 15-20 hours a year. Impeller still looked pretty good, no missing fins. I have an impeller puller but that did not work. Ended up taking the water pump off the fly wheel to work on it in a vise.
Tried letting penetrating oil sit over night and still did nothing. Put the pump in a vise to pull with 2 Vise Grips and still stuck. Also hit it with a hammer and punch on the inside of the impeller core but that did not break it loose. So I ended up using a wood chisel to cut slices down the rubber of the impeller and removed all the rubber off the core.
I did not have any short thin saws-all blades so cut down a shorty with a regular tin snips. Carefully cut trough the core about 80-90% thru the brass so not to hit the splined shaft.
Split the core of the impeller with a hammer and screw driver and it popped right off. After the core came off I inspected the splined shaft and could not find one mark on it from the saw blade. I did use some anti seize on the shaft but after a couple of years it may not keep it from doing this again next time.