Impeller / Water Pump should be replaced every year or two. Does not include impeller plate which does not need to be replaced every time.
Sierra Marine Replacement Ignition Coil. You need one coil for each cylinder. Old coils often become cracked or disintegrate over time because of the epoxy sealer originally used. New coils made with different materials are much more reliable than the original.
You will need one of these for each cylinder.