Hey guys new to the forum and looking for a little help. My father and I currently own a 1996 Stingray 609ZP 4.3L Merc with Alpha One out drive. Boat only has a total of 330 hours and is clean inside and out. The original owner said he had the outdrive serviced a few months back (around december) prior to us buying it in June. We have noticed a vibration noise coming from the out drive mainly heard when flushing the engine, nutural or drive above around 2g. Outdrive being fully down by the way. You can also hear it when we are boating but its a lot less subtle probably due to it being in the water. We can not feel any vibrations through the boat but the noise is hard to explain, again like a vibration/buzzing noise. My father had the boat out today and said it seemed to be getting louder but I was not out for the ride to verify.
Possible causes or where to start looking? My guess is that it has something to do with the u-joints (if thats the correct name) as it sounds like an unbalanced driveshaft in a RWD vehicle, if anyone has experienced.
Any help would be great! We are very mechanically inclined and don't have any problems tearing into the drive if it sounds necessary.