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 On Dec 13, 2016, at 8:50 PM, Jeremy Ralph via CnC-List <[email protected]> wrote: > > Yep, the mighty Yanmar 2qm20 is raw water cooled and the 1978 original. My > understanding is that the thermostat opens to route salt water through the > block when warm enough. > > Thanks, > Jeremy >> Dec 13, 2016, at 7:38 PM, Rick Brass <[email protected] >> <mailto:[email protected]>> wrote: >> >> Jeremy; >> >> Someone has probably pointed out in a later post that – unless you have an >> older RAW WATER cooled engine – the water that passes through your sea >> strainer never sees the inside of your engine block. >> >> If you have a fresh water cooled engine (most Yanmars have an F in the model >> number) the antifreeze you put in the strainer protects the strainer, the >> heat exchanger, and the muffler. The engine already has antifreeze in it, >> just like your car. >> >> Rick Brass >> Washington, NC >> > _______________________________________________ > > This list is supported by the generous donations of our members. If you wish > to make a contribution to offset our costs, please go to: > https://www.paypal.me/stumurray > > All Contributions are greatly appreciated!
_______________________________________________ This list is supported by the generous donations of our members. If you wish to make a contribution to offset our costs, please go to: https://www.paypal.me/stumurray All Contributions are greatly appreciated!
