I had my 1961 merc 400 lower unit rebuilt a week ago my outboard mechanic even put a guarantee on the unit that it should last a long time unless for some reason i was to get fishing line tagled into the prop.I just took it out on the water and the thing didnt spit water and overheated within about 2 mins. could i have put the unit on wrong when i reinstalled it? or could the copper water line be clogged? i attempted to pu a line through the pee hole but something in the motor is stoppin the line. I even tried a clothes hanger but same thing stopping it. I think it may be the casting in the motor. what else can i do to check for a clog?