Bravo's are cheap............run it till she blow's.......lol.............so what does the Cert. Merc guy say ??

U-jouint hitting the inner bellows race ? IDK cant tell on the inner web

Run it then until it becomes silent!

:I have been running it...runs great..no vibs..shifts crisp..I don't get it...I had it taken apart too many times...I will run it until something sticks out of the side. thanks for all the responses...my merc guy??? says nothing.

The inner bellows race...do you mean the ring that keeps the bellows snug against the bell housing?

Maybe its just the clearances stacking up when you run it on the trailer? There is no load on it then. How does it sound when in the water?

no sound like that in the water

yes, you stated a certified mercury guy rebuilt the the drive, thats who Im referring to

He has no answer now, first he said it was the u-joints rattling..so i changed the complete input shaft from a Sierra to a OEM Mercruiser.. no change in noise

[QUOTE=35fountain;4640845]I sent 6 videos to Mercury Marine..They said they couldn't hear it from a video..But they said check the top cap bearing and if you haven't ever changed it, you should just be careful on the tower height. Also make sure the + - are lined up perfectly on the gears. top minus bottom plus or visa versa, and something about the shift linkage adjustment. They also mentioned something about when the engine comes around on the compression stroked it actually slows down and speeds up even if we don't hear it and even though the engine is spinning smoothly it can cause a rattle, an engine that is tuned differently or needs to be adjusted. I told him I have 490 hp and i have the only boat out of 12 performance boats in my marina with this noise and the other 12 boats have a lot more hp than i do.They mentioned boats with transmissions that have a clutch plate rattles. I believe i mentioned something about this in a prior post. I swapped the drives and the noise followed the drive. My other drive is quiet, so i will cut out the rotation of the engine diagnoses.
Took the boat out yesterday...no vibrations..Hit some big rollers, came out of the water a lot.. Put the boat on the trailer, started it up and the noise was a bit louder I guess from the oil thinning out.

Well, thanks for all the input from everyone..It was a good try..Hopefully the drive stays together.

I personally don't think you have a serious problem. Probably just a little light on preload somewhere. I would just run it and not worry about it.