I have a 2054 Pro Drive with duals on it. I took it out a couple weeks ago and one of the motors started acting up. The motor revs fine in idle but when you put it in gear and rev it up the motor bogs down and backfires (when in water). I took it to Pro Drive and they cleaned the carburetor and reseated the valves. Took it out this weekend for the first time since I got it back and it started doing the same thing after about 4 hrs of running. Any ideas??? The motors are 2013 36's.

Plugs, air getting into in the fuel line somewhere, intake leak just for starters

I checked the plugs independently and they seem fine. Disconnected one at a time and engine ran. They did a leakdown test at Pro Drive and removed the heads, recut the valve seats and lapped the valves. How can I test for a leak in the fuel line? I did notice at one point today that when the engine killed I could not restart it right away. I had to reprime the bulb before it would start.

Check the whole fuel line for any gas residue, then check all connections, and make sure the clamps are tight. Then check any plastic fitting and filters for cracks.