I bought a used 1994 Mercury Tracker, 3 cyl. 60 hp motor last November. Oil injection pump has been removed. I've invested about $400 in it, adding / replacing little things worn or missing. My efforts have included rebuilding the three carbs, replacing the spark plugs and wires, and verifying the timing was correct. The motor starts and runs, but with a rough idle that carb adjustments don't correct. Big problem though is, when motor is accelerated to approx. half idle, I can hear metallic clunking sounds coming from it, especially when I back off the throttle. There is no apparent engine miss or decrease in rpms accompanying these sounds, but I'm only running the motor in a barrel w/o a prop. This is my first outboard motor and, while I?m familiar with car engines, a two-stroke is new to me. I'm really concerned over the metallic clunking noises I'm hearing though. Compression on all three cylinders is very close to 110. What do you think my problem might be?