Block Heater Thoughts
There is a major advantage to using very low wattage heaters that need to operate at much longer duty cycles vs. a typical Cummins or KIM Hotstart types supplied block heater that uses a thermostat or timer to control heat……………….It’s the overall safety of the system in a moist salt laden air environment..
All heaters are resistance devices and turning on and off using a typical 1000-1500 W heater creates high electrical surges (2-3X) at the plug connections you find in your boat or at the dock connection.. All you have to do is feel the heat at the plug after a day or so,, Then as time going on, it just gets worse as the resistance increases at that connection.. Building resistance is a fact of life with every electrical connection in a typical marine vessel and the higher current flow thru that connection, just increases that resistance………….. Kinda a vicious circle.
Now, use a low wattage heater that can transfer that heat slowly by CONDUCTION thru the heat sinking abilities of the oil pan/engine mass, sized in the 250W per 2000 lbs of cast iron range, and even though the heater may need to operate at between 50 & 100% of the time, long term use in this nasty marine environment has proven to me over the past 20 years that this is a much safer way to go…………Maybe 15 years ago I tried to use 240V 1500W coolant block heaters at lo to accomplish this by running them on 120V and it worked very good, but in the end, that was just too complex and expensive……….I switched over to low wattage oil pan heaters that stay on most of the time and I’ll never look back.. Too simple, 100% long tern safe, and way cheaper..
In the end what you are trying to accomplish is to keep the engine mass 20-40 degrees F above ambient air temp outside the engine room.. How you accomplish that is your call, but well over 25 years of doing this has taught me much– I prefer the slow, much safer, much simpler, and low wattage or “Softer Way” to accomplish that.
Tony
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