There is a bypass port in the thermostat housing that allows a limited amount of water flow through the engine block and cylinder head prior to the thermostat opening. This is to prevent getting localized hot spots while the engine is warming up. So some of your antifreeze gets into the block so long as the engine is running.
Are you sure it is a 2Qm20? I have a friend with a 1983 C&C 29-1. It has the original engine in it, which is a 2Gm13F. I had the impression that the QM was a replacement for the GM. From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Jeremy Ralph via CnC-List Sent: Tuesday, December 13, 2016 11:51 PM To: cnc-list@cnc-list.com Cc: Jeremy Ralph <jeremy.ra...@gmail.com> Subject: Stus-List freeze proofing 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 <rickbr...@earthlink.net <mailto:rickbr...@earthlink.net> > 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
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