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!

A lot of times these weird electrical issues are bad grounds. I would start from the negative post on the battery, and work your way from there cleaning connectors along the way.

Yea that was my first thought. I've been through the connections but it is hard to test when the boat is on the trailer because it runs perfectly when it's on the trailer.
Thank You