My 74 Ted Williams 7.5 hp can either run fine or start and die quickly. I recently put a new fuel pump rubber in the carb and replaced the float bowl valve and float attachment. In my yard it ran great. When I had it on the water it would start but not run for more than a few seconds. At home the next day it was fine again. I don't understand how the fuel gets from the tank to the engine. It has the original fuel tank. In the cap there is a screw to open a vent. I believe that should be open when running. Is that correct? Should I just have to open the vent and give the bulb a few squeezes until it is firm?

Also how much water does it need to be in when running on land? Is a bucket on the bottom foot of the engine sufficient? I read somewhere there is an inlet hole behind the prop to let water in the cool the exhaust. Is the inlet on the bottom or higher up the engine. The exhaust exits on the top of the shaft. There are two holes pretty far up the shaft.