I have twice had the cutlass bearing replaced on our 321, but I was never aware of any noise made by it.
The first time I did it on a precautionary basis because there was a bit
of play evident in the bearing when inspected on the hard.
The second time was two years later because the bearing started coming apart – the inner rubber separated from the bronze tube.
Both times the work was done by professionals, in my case Yachting Sports at Hamble Point who commission new Nauticats.
I do most of my own maintenance but replacing the bearing is not for the faint hearted in my view.
I believe YS removed the prop. However rather than then disconnecting
the prop shaft from the coupler/gearbox and removing it, professionals
have a tool they put on the shaft and then drive the old bearing out of
the P bracket using a hammer and brute force. My bracket has one grub
screw which they removed. Then they drive the new bearing in on the
Bearing are readily available from marine suppliers. I bought the second
one myself from Aquafax. You just need to know the prop diameter and
the bearing length. They come in a range of standard sizes. There are
now composite ones available as well as brass.
A.S.A.P. Supplies are another supplier – http://www.asap-supplies.com/marine/shaft-bearings-for-propeller-shaft-and-rudder-shaft
Finally se the posting under Boat Jumble and Crew about 331 bearing.