My buddy bought a 92 29ft fever with the black 502. This wečkend was the first time having it out. Started out running bad, couldn't pull more then 3000rpms and started cutting out. We figured bad gas as it has been sitting a year. Well 2nd day out we were idling and all of a sudden it just started clanking around. Sounded like it dropped a valve. My guess was maybe it wasn't bad fuel and it jumped time. The motor only had 386 hours on it. These motors have any issues? What's your guys thoughts?

First thing I would do is pull/inspect the plugs. If none are damaged, do a compression test.
Sure sounds like valve let go.

Did he buy it without a Sea Trial??

Sounds like they bought it without even hearing it run if he wasn't sure about bad gas. Ron was telling me the other day he had a guy call wanting him to work on a MTI he had just bought. The port motor wouldn't crank. They changed batteries and still nothing. Ron told him yes bring it around. The guy gets the boat around to his shop and he checks it out. Turns out the motor was stuck. Ron said the guy almost broke down crying saying he had just bought the boat and had paid over $200,000 for it. Ron said well guess that's not a bad price if that's all is wrong with it. You want me to check the rest of the boat out before we get into this motor? Guy said please. Ron went over this thing and the other motor had water on the top end and both drives were stuck. Ron was like what the hell do people think about? How do you spend that much money on something and not invest in paying a decent mechanic to go with you and look things over. Or at least what you just said Jake. Just a ride up the river and back. Best of luck to you brother. Hope this doesn't turn into a night mare for you!

Well it's not mine, I had mine surveyed and compression check done. He did go for a sea trial and had marina no compression check before he bought it. All was good until his first day out with it by himself.

I had one of the Black engines years ago, one day immediately on start up it dropped an exhaust valve seat, same banging as you say, i immediately shut it off, only damaged one piston, the seat just fell out, it had ran perfect for years w/ no warning.