I have a 1983 Mercury 25hp. Just replaced gears in lower unit.Also replace water pump impeller as directed in manual. Upon testing in a tank the telltale stream is intermittant. Also bubbles coming from a couple areas in lower unit(by 2 rear bolts that hold the lower unit on). Maybe the bubles are normal and I never noticed it before. but the main concern is the water pump issue. Thanks for any advice other than dropping the lower unit and starting over on the impeller which I'm afraid is the only real answer.