"I have a BMW 220 petrol engine coupled to a BMW MKII stern drive in my 23' cruiser.
I have replaced the unis and the gimbal bearing because I had what sounded like a rattling set of unis.
When I put the new ones in it was good for a few hours now the rattle is back bad as ever.
Only rattles after a hard run when you come back to idle speed or neutral. By tilting the leg up a little at idle the noise disappears, but will return when you increase engine revs to 1800 rpm.
Things I know are. The unis are new and I was extra carefull to make sure no rollers dropped during assembly. I double checked the circlips were all secure and greased them well.
The gimbal bearing is new and the bellows is new and watertight.
The splines on the transom output shaft and the gearbox input yoke seem a nice fit and were liberally greased.
The engine mounts seem good, even with sudden hard accelleration.
Things I dont know. The engine allignment checking procedure. The state of the coupler plate and or flywheel.
And since I have only owned the boat since last October I have little history of what has ever been done.
It is about 18 years old.
Thank you for reading this post. Anyone with anything they think will help please post.