How to Clean a Marine Heat Exchanger

A marine heat exchanger, also known as a "keel cooler," serves the same purpose as the radiator of an automobile. The biggest difference is, while a car's radiator dissipates the heat generated by the car's engine into the air, the keel cooler dissipates the vessel engine's into the water. Both contain a form of antifreeze poisonous to animals and hazardous to humans, which means that purging and cleaning your boat's heat exchanger are potentially harmful to pets and the environment. With a bit of care, though, you can avoid the cost of hiring this chore out.

Things You'll Need

  • Biodegradable marine descaling compound (liquid)
  • Diaphragm pump
  • Two hoses, 5 feet in length
  • A large (5 gallon or greater) plastic bucket (catchment bucket)
  • Disposal drums suitable for glycol-based coolants (can be obtained at a marine disposal facility)
  • Fresh water hose
  • Adjustable wrench
  • Combination wrench set
  • Purge the heat exchanger of glycol-based coolants with fresh water. Dispose of the coolant in the drums you acquired from the marine disposal facility.

  • Clean the outside of the heat exchanger first. Spray the outside of the heat exchanger with undiluted liquid descaling compound and allow it to stand for 10 minutes. Rinse with fresh water and repeat this process four times. Use the final fresh water rinse to remove any loose trash or waste.

  • Clean the inside of the heat exchanger next. Attach the hoses to the diaphragm pump and mix fresh water and liquid descaling compound in a 50/50 mix. Attach a hose to the suction side of the diaphragm pump, and put this hose into the catchment bucket. Attach the other hose to the outlet side of the pump and to the hot engine jacket water inlet.

  • Fill the catchment bucket with the 50/50 mixture of descaling compound and water. Turn the pump on and allow the descaling solution to circulate through the heat exchanger for 2 to 4 hours, then turn off the pump. Dispose of the descaling solution.

  • Fill the catchment bucket with fresh water, and turn the pump back on to flush the system for 15 minutes with the fresh water. Dispose of the water in the catchment bucket properly and refill the catchment bucket with fresh water. Repeat the flush procedure for 15 more minutes, then properly dispose of the water in the catchment bucket. Reinstall the heat exchanger on your boat and recharge.