Diamond marine built with their fuel system. Both motors run and then shut off. Happens at idle and have died at 4000 rpm. They crank and crank but wont re-fire until they sit for an hour. Both batteries are charged and in good condition. Tried a jump box after one died and all it did was crank. Fuel is clean and water separators are new. Plenty of fuel in the tanks. Reeds are in perfect condition. Where should I start?

It sounds like something heat related. Have you checked to see if you are getting spark when it happens ? That would be the first thing I would do but I dont know how hard that is an an outboard. What is there in common to both engines that would cause them to loose ignition ?

How is the fuel fed to them ? Anything in common there ?

If both engines are always stopping at the same time you have to look for something that is used for both engines.

Just thinking out loud