1988 Checkmate 454 Mag

Hello I am new to this but I have a 1988 Checkmate Vision with a 454 Mag. I am having an odd problem... I put the boat in the water and after running for 10-15 minutes she dies. She will start right up but then almost immediately start running rough and then dying out. He is the odd thing, when I start it and it's running rough if I hit the trim switch it fires right back up like nothing is wrong. Then If let go of the trim switch it dies again. Definitely electrical and I have checked every wire twice but can't figure it out. So frustrating!! It will run like nothing is wrong in spurts but eventually dies out unless I hold the trim switch. Very odd, any help would be GREATLY appreciated!