I recently purchased this 73 Evinrude 25 and took it out today. Motor runs great, starts fast, but, after pulling out, I noticed the hood was very warm. Pulled the hood and there was (some) steam rolling off the motor. Seemed to be pumping great while running, but it was also very hot to the touch. Brought it home and pulled the thermostat out and it was bone dry inside. Could have evaporated I guess, but I had the thermostat out about 30min after pulling it out of the water. What could cause this??? Thanks B.C.