Thanks Rick for explaining. I wish I had a freshwater cooled engine. What I've got is a raw water cooled engine though. There is no heat exchanger or coolant. Salt water flows thu
On Dec 13, 2016, at 10:20 PM, Rick Rohwer <[email protected]> wrote: Hi Jeremy, The water (coolant) inside the freshwater cooled engine is controlled by the thermostat. Coolant is approx 50% glycol to reduce the freeze point of the coolant (-25F or more). When the engine hits the set temp (190F), the thermostat opens and allows coolant cooled by the heat exchanger to enter the engine. No raw water should enter the engine block. Think of the heat exchanger as a radiator. The amount of raw (salt or fresh) water is controlled by the speed and capacity of the raw pump, controlled by the rpm of the engine. It is belt driven. It also continues on past the heat exchange phase to be dumped in to the path of the hot exhaust, thereby protecting the muffler and exhaust system from melting. This system accomplishes the same thing as you are describing but changes the freeze protection plans. For freeze protection, I think most folk feed glycol solution into the raw water pump until they see it exit the exhaust and then shut it down. My boat sits in 45-43F seawater virtually all year. I don’t sweat the freeze cycle on the engine! It would have to get really cold for a very long time. I would bet the 2QM20 is a mighty warrior of an engine. I have the FEARSOME 3HM35F! Happy sailing! Rick Paikea- 37+ Tacoma, WA
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