superboat1982

Hi All. I have a Bravo One drive w/50hrs on it that’s making a rattling noise at idle. When on the hose the drive sounds like it has a marble rattling around in the top end. The noise stays the same when going into and out of forward or reverse or when turning the drive from right to left, however, it does stop making the noise when I raise the rpm above 1000rpm. Boat has thru hull and silent choice exhaust. Any thoughts?

AngerMgmt

Could be the divertors in your silent choice. Switch your exhaust thru the prop and see if that changes it.....just a thought.

tssteph

ditto.... Exhaust flaps. Two broom handles will likely solve the problem.

superboat1982

I tried turning on and off the slient choice yesterday with no change but didn't try the broom stick trick. I assume I use the broom handles to push against the silent choice diverters when they are closed( thru prop) so they can no longer vibrate with the exhaust pulse? Also are there any flaps in the Y pipe that may cause this? Thanks for the quick repsonses

HiPerf2000

iTrader: (2)

yes....there are flaps in the Y pipe.

Could it be a u-joint noise ? is your drive down while you are testing ?

superboat1982

The drive is down when I'm running the boat on the garden hose. However, I just found out that my brother has been running/flushing the boat with the drive up for some time now. The interesting thing is that the ujoints seemed fine ( smooth and tight when turning the yolks) when I check them.

firehawkcat

There is a bearing in the top cap, it is probably what you are hearing. Mine does the same thing at idle.

superboat1982

I'm assuming it's something that needs replacing so I will pull the top cap off and check to see if that bearing shows any sign of wear. Question: I do have another bravo cap(with a bearing inside) from a mid 90's drive that I use as a spare...would that work with my 2006 sweptback drive just for a quick test at idle?

Mr Gadgets

No it wont work.. different animal all together.
Have you put your hand on the top of the drive when it rattles? The shift fork bounces up and down as the bump rings spin by and move up and down. If you pull the top cap and dont see any metal or damage, and the ujoints are solid and smooth.. Then it is more than likely the shift fork and it is normal. Mine did it for years.. and never had a problem.
But if something looks bad, then dig deeper.
The top cap from the 90's and the new ones have differnt lenght towers and different depth to the shim floor. Don't try to interchange them. You can put a new cap on an old drive if shimmed properly.. but not the other way around..

Dick

superboat1982

Mr Gadget thank you for the explanation. I did place my hand on the top cap and all around the drive. The vibration seems to be coming from the top of the drive but I can also feel it on the bellos( where the ujoints are) . Not sure if the vibration is being transfered from the top cap to the bellows or other way around. I will remove the top cap and check for potential issues and I may pull the drive one more time to double check the ujoints. I know the gear oil is good as I change it every season.