[C320-list] noise

[jim brown]

Was motoring to Kingston Ontario yesterday and about half way there (12 miles) noticed a whistleing noise at about 2200rpms. Seemed to go away at 2800 but could be heard at lower rpms. It was hard to pinpoint but I removed the front and real engine covers and heard nothing, checked the shaft and packing gland nut which was cool and leaking normally. The transmission was quiet. I opened the rear lazarettes and the whistle/warble was quite loud. Went into the compartment and it seemed to be coming from the bottom area. While sailing back home today I left the tranny in neutral and there was no noise. It also doesn't happen in reverse. Could this be the sound of a failing cutlass bearing or are there other possibilities. Hull 978 with 200 hours on the engine. Desafinado will be hauled in 2 weeks for the winter but I was wondering what to expect or have checked over the winter lay up. Thanks for any help.  Jim Brown