[C320-list] Noise from shaft packing??

[Larry & Melissa]

Has anyone here who is using the GFO shaft packing noticed a high-frequency noise at certain engine rpm (1500-2000)? I just noticed this noise this season and am wondering if the switch to the GFO could be the culprit. The new packing and the installation of a new strut bearing were the only drive-train changes made over the winter. I don't see how it could be the strut bearing, though I suppose anything is possible. The noise also occurs when sailing with the prop free-wheeling when I hit around 6-6.5 kt (which I assume has the prop spinning at the equivalent of an engine speed of 1500-2000 rpm). It is difficult to pinpoint the source when down below. It almost is louder in the cockpit. It could also be transmission related although the transmission seems fine in all other respects. Any thoughts or experiences with others using the GFO are welcome.

Thanks,

Larry