Take a look at the wiring plugs on both engines. The 220 seems to have two yellows for the alternator, two wires from the exciter coil, two from the trigger coil and a green and a red/white from the gearchange for neutral and reverse lights. If your 250 is the same, it should be an easy swap electrically. The 300 was DC ignition which is a whole different set up, but I think the 250 was AC, like the 220.