The last couple of times I've been boating, while making a turn at about 3500 RPM or higher, the engine sounds like its running faster than the prop! The boat seems to be losing power, but once out of the turn the prop seems to catch up with the engine RPM. Is this cavitation or a problem? I/O, single prop, V6, --trim set about 1/4 up from full down position. Volvo Penta.