Hey Bill,
I'm glad you are having success with the Mezon.
These motors do run cool, but the 650 runs quite a bit cooler than 600.
155F does seem a little hot for a 55F day. The 650 is very robust to installation, but the 600 is not as robust. You may need to get more airflow over the motor, or consider switching to a 650.
Brenner ...