A couple of thoughts, as I did some pretty extensive testing on motors a couple of months ago, including measuring starting and ending temps using the laser thermometer...
Under "normal" or "average" loads, the motor should be finishing the flight not much hotter than 120-130 F, assuming it is well ventilated. It will feel warm, but not uncomfortable for most people; definitely not burning hot. If it is hotter than that, the prop load (pitch, diameter, RPM) is too high for the motor, which means you are trying to fly too much of an airplane on too small of a motor. Since you did not post any specifics, it is hard to evaluate that part.
Looking at the picture, the motor itself is not very well ventilated at all. The oncoming air stream is being sliced by a large solid spinner, much larger in diameter than the motor. The spinner leaves a certain area of low pressure air (a sort of vacuum) behind it, making it difficult to cool the motor. Leaving the battery hatch off does help to evacuate the escaping air, but if the oncoming air is blocked (by spinner and motor mount bulkhead), then it doesn't help much.
Suggestions: (1) please post details of your setup - battery, motor, prop, RPM, airplane data - area and weight, line length, lap time; (2) consider using a vented spinner.