I recently had my 1998 4.3 liter, mercury alpha outdrive worked on. The engine was a complete rebuild and the impeller and bellows in the outdrive were replaced. During the first 10 hours of running there was nothing unusual, but during the last run there is a whirring noise, like a small motor running (but it's not the bilge pump or live well motors). We can hear it most clearly when standing on a dock behind the stern. I don't know if this is relevant, but the bilge pump malfunctioned on the trip before this and the engine compartment got enough water in it that I could see it churning at the rear of the engine for about five minutes until I got it back to the ramp. All gauges read normal.<br />Thanks.
