Yes
Growth on the prop particularly and on the bottom in general will definately rob power (or more accurately performance) and cause the engine to smoke due to the excessive strain on the engine. Clean it and I bet you'll see an improvement. The black smoking at full throttle may indicate some carbon build up. Deisels need to be run regularly at about 75% of rated RPMs ... regular running at low RPM causes carbon build up which may be what you are seeing when you rack it up. When I bought my '88 35 1 1/2 years ago, the previous owner had never run the motor at over 2000 RPMs (for an engine rated at 3400) He thought it was bad for it but the opposite is true. Consequently, for a while, when I ran her at over 2000, it smoked terribly. Over a period of time, running at higher RPMs, the smoke cleared out. I now run her at 2600-2700 and its virtually smoke free. Before I shut her down, I rack her up for about 3 seconds to blow out any build up. I believe this is Yanmar recommended procedure. The engine runs much less smoky than before. However, if your engine continues to lack power even with a clean prop and bottom, more severe coking of the exhaust system may be indicated which will need to be cleaned.