unknown yamaha 25hp engine repair

[Kylester]

i picked up a 25hp yamaha 2 cylinder 2 stroke engine for cheap was told it needed a water pump impeller when i tried to undo the shift linkage it just spun and i couldn't undo it when i unbolted the lower unit it just fell out i wouldn't have a clue where to start. heres the engine number ( 25DM 695 S 032281 )