[C320-list] Transmission or prop noise

[Chuck and Kathy Mueller]

This year, I developed a noise in the drive train.  It's a high pitched noise at most engine rpm's, but it goes away at low speeds and at high speeds.  I'm hearing it in forward at about 1500- 2800 rpm, when motoring.  I can't duplicate the noise if Irun the engine up in gear when tied to the dock.  I've checked alignment and it is very good.  I thought that this might be prop harmonics from my three blade fixed prop as I cleaned the prop last spring, but I don't really have any rounded trailing edges per the post a few months ago.  A neighbor told me that the Yanmar (Kanzaki) transmissions can do this due to wear of the cones.  Anyone have any experience with transmission noises?
Chuck Mueller
C320 - 2000
Northwind #676