While the rear cover was off I noticed a knocking from somewhere down the back of the drive shaft in my 04 XPDI (ski was only idling on trailer in the water at boat ramp).

Any ideas? bearings? I was contemplating hooking up my grease gun to the grease nipple on the seal carrier however I don't know what grease was put in it at the last dealer service (6 months ago) and I heard somewhere not to mix different marine greases.