Rattle from back of motor????
 

Just ran boat for second time with new motor. When loading boat back up at landing i had the hatch up and noticed a rattle coming from back of motor somewhere. Breifly looked and couldnt see anything with the eye moving that would cause a rattle. Motor idles around 980-1050. When you put it in gear it gets a little worse and as you throttle up it will gradually fade away by 2200rpm. Could this be a gimbal bearing? Also i was told by a local performance marine guy that 1000rpm shifting would be ok? Im at a loss here!? This thing is so close to being spot on but it seems like gremlins keep creaping out. When motor went back in it was properly aligned with alignment tool. Boat is an 07 and has 140 actual hours. I have never replaced gimbal bearing so to my knowledge (second owner as of 68 original hours) its the factory installed bearing. Boat has a Bravo 1 outdrive 1.50 ratio. Help or guidance would be awesome!

Also doesnt appear to sound like and internal or valve train problem.

Also B1 is a swept back newer style

Thru hull exhaust?
Internal flappers in exhaust? They love to rattle.

Good point. Possible ujoint or gimbal bearing. To OP do you notice any difference when raising/lowering drive. Have you tried greasing the bearing at all? I'd try getting idle down also. Bravo 1's tend to frown on 1k plus rpm's long term.

If you don't isolate it soon you might want to inspect upper gear case. Otherwise possible couple? Wouldn't think so but?

No internal flappers. Im running dry to tip so i only have an external flapper. Thought maybe coupler or flex plate? I guess im on border line shifting rpm but it sounds like something "heavier" trying to move or is moving. Im going to pull valve covers and check all rockers and retighten my stainless marine manifolds but it's something off the back of the motor but it has me 100% stumped. Just started doing it at an idle while loading up at landing ramp earlier today

Ill grease and check tomorrow on the hose. I had also thought possible u joints since this motor makes about 300 more hp than the boat came from the factory with

If its any help and i just remembered this. My trim indicator when the drive is all the way down and also when cruising up to mid speeds acts correctly but once i lay into it and trim it on out it jumps all over the place and will not show correct trim? It has only done this since we put outdrive back on. Never did it before?

You need to pull the position senders and tighten your hinge pin. Ck bushings also.