Last weekend I helped a friend troubleshoot some issues he was having with his older 65hp Mercury outboard motor. Whenever he pumped the bulb to get the fuel lines filled with gas, the gas started spraying out of both carburetors. Too much pressure seemed to be reaching the carburetors in the float bowl.
We took apart the fuel pump and did not find any holes. After some more inspecting we concluded that it was probably time to replace the old cork floats with new plastic floats. We did that, put the parts back together, filled it up with fuel and Mercury outboard oil, and then gave it a go. The new floats seemed to do the trick!