Niall;
Whether you need to bring your Yanmar engine up to temperature before putting in antifreeze depends on whether the engine is raw water cooled or fresh water cooled. In a raw water cooled engine, water from outside of the boat (raw water) is pumped through the engine block and cylinder head to cool the engine, then to the exhaust riser to cool the hot exhaust gas, and is then forced through the muffler and out of the exhaust outlet by exhaust pressure. The operating temperature of the engine is governed by the thermostat, which stays closed until the engine reaches operating temperature - generally 165 F - 180 F for a diesel. There is a bypass (which may simply be a small hole drilled in the thermostat or a small passage cast in the thermostat housing) that permits a small amount of cooling water to "bypass" the thermostat and flow through the engine to prevent hot spots and cool the exhaust gasses. You need to bring a raw water cooled engine up to operating temperature for the thermostat to open so you can get antifreeze into the engine block. A fresh water cooled engine has antifreeze/coolant in the engine block already, and a "fresh" water pump circulates the coolant through the block and head, on to a heat exchanger where it is cooled, and then back to the water pump. A second "raw" water pump brings water from outside the boat, sends it to the heat exchanger, and then to the exhaust riser, muffler and exhaust hose & outlet. The plumbing of a fresh water cooled engine is just like your car engine, with the heat exchanger taking the place of the car's radiator and using cool water instead of cool air to cool down the hot coolant. Since there is already antifreeze in the block of a Fresh water cooled engine and the thermostat has nothing to do with the flow of raw water, there is no need to heat up the engine. You only need to start it so the raw water impeller can pump antifreeze through the heat exchanger and exhaust. Your mention of "Plumbers" antifreeze brings up something else that everyone should consider. Plumbers Antifreeze is propylene glycol. It is intended for use in potable water systems (water tanks, hoses, etc) because it is safe for human consumption. It is commonly used in sink traps and drains because it does not expand as it gets colder (unlike water) and will not break pipes. Plumbers antifreeze does not freeze, it turns into a gelatinous slurry at reduced temperature. So there is no "freeze point", but there is an "expansion point" at about -50 F (-45 C) when the jelly starts to expand and may break pipes or burst hoses. Now the -50 F expansion point is for 100% propylene glycol. If it mixed with water in the system, the expansion point can be quite a bit higher depending on the concentration. (IIRC, a 50% mix of water and plumbers antifreeze starts to expand around 0 F.) Plumbers antifreeze also breaks down when exposed to heat (say much above 100 F) and should never be used for coolant in an engine. Conventional antifreeze is ethylene glycol and water mixed together. A 50/50 mix results in a freezing point of -34 F (-37C), and a mix of 70% glycol/30% water freezes at -90 F (-68 C). (How you can mix something that freezes at 32 F with something else that freezes around 0 F and get a solution that freezes at -35 F is one of those things I learned in high school chemistry class but never fully understood. Guess that why I was an ME not a Chemical Engineer.) Conventional antifreeze has anticorrosive ingredients, lubricants for the water pump, and sometimes leak inhibitors as part of the mix. That would be the preferred antifreeze/coolant for an engine. I'd wager that your 35hp Yanmar is a fresh water cooled engine, most recent diesels are. Yanmar is pretty nice about putting an "F" in the nomenclature for fresh water cooled engines (3QMF30, or 2GM20F) so that may tell you what you have. The presence of 2 water pumps (a conventional belt driven pump on the front of the engine plus a Sherwood or Jabsco raw water pump driven by a second belt or a drive off the camshaft) is an indicater. Or you might look for a heat exchanger (though I think a lot of Yanmars have the heat exchanger coils integral in the exhaust manifold, instead of in a separate unit outside the engine.). I hope this answers your question, and doesn't bore you enough that you want to drink some ethylene glycol and end it all. Rick Brass Washington, NC From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of niall buckley Sent: Friday, November 29, 2013 4:02 PM To: cnc-list@cnc-list.com Subject: Re: Stus-List Winterizing - putting oil in the intake Hi Rick, Thank you for that helpful article. I have a question for you. Really, I should be able to figure the answer out based on all of the back and forth on winterizing. Anyway, here is the question. My engine is a 35 HP Yanmar. I live in Nova Scotia where the winters are relatively mild by Canadian standards. However, once in a while they can be brutal. My winterizing has always been very simple ; remove hose from raw water intake, point it to the sky, insert funnel, start engine and pour about 2 gallons of plumbers anti-freeze into the hose (which goes to the impeller), end of story. Rick, I've done this, for several years and it's worked just fine. Should I be worrying about getting the engine up to temperature (is this even possible, out of the water, with no load on the engine ?), so as to allow anti-freeze into the engine block. Then, there's all the comments about getting water into the block. Can you help me with this ?
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