200 opti cuts speed and dies while under load...

[Lizzy K II]

I'm completely stumped on what could be causing my motor to die out after about a minute of running under a load. I've checked all fuel pumps, filters, and for leaks. fuel pressure stays up as well as air pressure. DDT does not find any problems. what Would could cause my motor to run normal at an idle and to die after running at a higher speed? As soon as it dies it will crank up again

[boats.net]

Fuel problems is the most reason for that. It could be an ignition problem or maybe even the main relay, hard to say unless it can be tested at time it stalls.