A-4 winter operations

Greets: Ran the engine today as normal to make sure everything is working fine and found that the water intake hose, strainer and water hose to the pump were starting to freeze up. Was wondering what solution other A-4 owners use to keep these lines from freezing overnight while operating their vessels under winter conditions. For now Ive put a ceramic heater into the area to keep things toasty however this works only while connected to shore power. Was wondering if anyone has worked out a solution that can be run from the batteries as shore power may or may not always be available. Best regards and thanks for any advise. -- /ch