Need advice about upper unit

"I have a Merc 454mag Bravo On

"I have a Merc 454mag Bravo One.

after starting it in my driveway the other day with ear muffs I noticed an awkward rattle coming from the drive. After putting my hand on the top of the upper unit i could feel the vibration and after running for about 5min a little above idle it was already pretty hot to the touch. The vibration also wasn't consistent but more sparatic , with varying intensity and frequency.

I did, by accident, start it with the drive up in the trailer position. I now know it's not good to do this but could this have been enough to cause stress and bind the universal.

i haven't checked my tranny fluid or my drive oil yet but my drive oil reservoir is full.

Please advise what would be the best course of action to diagnose my problem.

thanks"

"[b]"i haven't checked

""i haven't checked my drive oil yet"

Ayuh,.... That's Where you Start...."

I had this happen to me when I

I had this happen to me when I borrowed a friends boat years ago. Did the same thing........ran the unit in full up position. Made the same noise after too. Ended up stressing (cracked) the upper housing and chewed the teeth off of the upper gear set. Cost: Had to completely rebuild upper outdrive with new housing and gears. Took a loan out on my life ins policy.(not kidding)
Take the bolts off the upper bearing cover to look at the gears.....you'll get a better view than looking at the oil.