Idles but when you shove the throttles forward no power cuts out both motors. Put new plugs in both motors. Fresh 93oct from QT. Put new batteries in it. Still same thing. 355 Sterlings power fuel filters have about 400 gal through them. First time running it this year ran great when I parked it last year sat for ten months. Going to pull air filters off in morning try that. If that doesn’t get it I’m going to check grounds. Both motors doing same thing. Volt meters jump around little bit. Thoughts?

As the problem is with both motors I'd suggest checking the fuel system first for water in gas (left over from old gas) and perhaps ethanol residual build up in the fuel lines/fuel injectors (if equipped). How's your fuel pressure?

Put 5 bottles of heat in it today took it out same thing. Both cut out when you try to get on plane. It had 20gallons in it when I took it out last November 80 gal of fresh 93. Next thing is check fuel pressure. It is hard starting if it sets I have to let air out of the fuel rails till I get fuel then it starts might be all the same problem? Both motors have me scratching my head. Grounds on the motors are tight battery cables tight.

What do they share ?
fuel tank ?
fuel tank pick up ?
power lead to ignition switches ?
etc/etc

Btw: describe ‘cut out’
I take that as they stop running completely.

If by chance you mean they start losing power, run rough, as you try to plane, but they stay running……if both engines share same tank, very possible you have some ‘bad fuel’ in there. I have run into this with a few different customers boat. Both where boats that get used each season, so not ones with very old gas.

Any chance the distributors have any rust or crap in them.

Common to both motors.....try the ignition kill switch....It ain't plugs, distributor etc....Like SB said common source like fuel.

Water in fuel most likely. Putting 80 gallons of fuel into a tank that has a few gallons of water in it changes nothing. The water still settles to the bottom of the tank. Heet is won't remove water and heet is just rubbing alcohol

Changed fuel filters, checked ignition safety switches, spark is good. Fuel is the same fuel I put in my Dodge TRX to pull it down 93oct. Checked fuel pressure 38-40 pounds. Put a new coil on port didn’t change anything.. Put heat in the gas still cutting both cutting out when you shove the throttles forward. Cuts out in neutral and reverse. What next?

did you check and tested the batterys? Or bad commun ground?