I just picked up a 16hp Go Devil used and it ran like absolute crap when I got it. I went ahead and cleaned the carb and had my small engine Mechanic help me tune it and it runs 100 times better. The problem is after running for about 10 minutes under load it will sputter and die unless I pull the tail out of the water. I have an electric fuel pump and figured it was flooding the carb so I rePlaced it with a 2-3.5 psi pump and it still did it. I’m running out of ideas and any help would be greatly appreciated.

It sure sounds like a fuel starving issue. What about fuel line restriction or a vacuum leak somewhere in the line or pickup