Buy a can of SEA FOAM
change the impeller
change the plugs
coils should be okay
drain the carb
change fuel filter if it has one
with the plugs out shoot some penetrant down each cylinder and let it sit over night
next day roll over the fly wheel with a wrench with the plugs out make sure the are free and moving
at this point if you have the means check the compression in each cylinder
change out lower unit oil
after all this is done mix a fresh batch of gas and try and fire it up with rabbit ears on
if you get it going stop it take the cover off the carbsfire it back up
and shoot some SEA FOAM down each carb intake
dont be alarmed it will smoke like crazy but its all good your neighbours might want to kill you though(mine have learned this is normal)that should be it it should be good to go
This is all easy stuff
the most difficult thing for this motor will be parts not impossible though
oh yeah buying the shop manual will be a real good idea