Yikes, thats not a drive train, it's a reef

Poor little Yanmar! I've sometimes noticed that my motor (same one) will smoke at 3000 RPM if I'm fighting a strong tide and/or headwinds. If I back off the RPM, it seems fine. The motor purrs at 3000 otherwise, so I assume it's not a prop issue. This has never made sense to me, as the motor shouldn't "know" what the opposing forces are. Right? They should simply make the boat go slower. Or, are the forces somehow "lugging" the motor? Hypothetically, if the boat was tied to the dock, shouldn't the motor turn effectively at 3000 RPM? Dock,
line, boat and dock
cleat failure aside of course

Someone please explain