I was out on a lake when something (I think a branch) got caught in my prop. The engine wound wide open for about 3 secs. My daughter said she saw the item get thrown from the rear into the air. After checking for any prop damage (none found) I lowered the engine and throttled up. The engine sounded like a clattering diesel truck. I brought the speed down to about one third and the noise almost completely stopped. The engine never seemed to lose any power, but I took it easy going in. I got it home and started it up (in neutral) and the engine ran like silk. I turned off the engine and left it in gear to check the prop - had good resistance and could hear the piston cycle. Did I damage the lower unit (gears)? 