Author: steveng Any of the heaters we have available can be mounted at ANY angle (upside down, sideways, etc.). The forced-air design of Xtreme Heaters makes them effective at any mounting angle, and allow you to direct the circulation toward areas of concern. Was this answer helpful ? Yes (1) / No (0) How long can I leave the Xtreme Heater in my boat unmonitored? Is it ok to set my heater on the floor and not put in the screws?