According to Workshop Manual

[M-Captain]

The winterizing method in the Workshop Manual for my Yanmar 2GM20F is to drain the engine, drain the cooling system hoses, remove the thermostat and pour antifreeze into the thermostat hole until it is full. My question is, if I have to remove the thermostat anyway, why would I not follow the manual's procedure rather than sucking antifreeze into the seawater hose?

 

[Ralph Johnstone]

Can you provide a copy of those instructions as it sounds like more than just a few misprints ?

As far as the cooling system which contains antifreeze (fresh water circuit) you want to make sure it's up to strength which will give you the required cooling protection (60/40 max.) and leave the system sealed. Never put 100% antifreeze into your engine or it will freeze around -15 deg. F.

I don't see the relationship you mention between the stat and any seawater connections. Yes, you do want antifreeze in your sea water circuit if you can't blow everything out with compressed air (use a cheap 12 V tire inflator). The usual method for protecting the sea water circuit is to remove the hose at the thru hull and then suck a bucket of antifreeze into the running engine.

What kind of low temperatures do you get in your area ?

 

[Tally Ho]

I just winterized my 2GM20F yesterday.

1) Check your engine antifreeze (the automotive type in the radiator) to ensure it is fresh and will protect your engine. Replace it if you are not sure.

2) Use the "pink" antifreeze to winterize the lake water intake part of your cooling system...I pour antifreeze into my strainer with the engine running (2 gallons) and pink stuff is running out of the exhaust.
The hose for my water intake is hard to get off the strainer, so I went to this method. On my old boat, also with the 2GM20F engine, I pulled the intake hose off the thru-hull, stuck it in a jug of pink antifreeze, and run the engine. Replace jug for a 2nd gallon of antifreeze.

Been doing this for years on 2 different boats, and engine is winterized fine.

Greg

 

[Don S/V ILLusion]

The winterizing method in the Workshop Manual for my Yanmar 2GM20F is to drain the engine, drain the cooling system hoses, remove the thermostat and pour antifreeze into the thermostat hole until it is full. My question is, if I have to remove the thermostat anyway, why would I not follow the manual's procedure rather than sucking antifreeze into the seawater hose?

Some people simply suck antifreeze into the engine from the intake hose when pulled off the thruhull NOT realizing that the thermostat isn't hot enough to open allowing circulation. They see colored antifreeze coming out the exhaust assuming it opened when it may not have in which case they feel good but haven't succeeded in protecting the engine. Read some of the comments in this and other similar threads to see how common this mistake is.

Doing as your manual suggests eliminates the mistake. The manual assumes people don't understand the system and makes winterizing "idiot proof".

 

[Tally Ho]

I stand corrected!

Maybe my t-stat is open because I warmed the engine to change the oil.

Greg

 

[Davidasailor26]

Some people simply suck antifreeze into the engine from the intake hose when pulled off the thruhull NOT realizing that the thermostat isn't hot enough to open allowing circulation. They see colored antifreeze coming out the exhaust assuming it opened when it may not have in which case they feel good but haven't succeeded in protecting the engine. Read some of the comments in this and other similar threads to see how common this mistake is.

Doing as your manual suggests eliminates the mistake. The manual assumes people don't understand the system and makes winterizing "idiot proof".

Wait, on a freshwater (closed loop, like the Yanmar *GM*F) cooled engine, doesn't the thermostat just control whether the coolant is allowed to circulate through the heat exchanger? I thought the raw water (what you replace with antifreeze during winterization) flows through the heat exchanger and out the exhaust no matter what.

 

[M-Captain]

My understanding was you had to remove the thermostat in any case to make sure the antifreeze got through the full raw water system.

 

[walmsleyc]

It sounds like the workshop manual is talking about the non-"F" model engines. As Davidasailor26 says, for the "F" models, the thermostat is in the closed loop side of the system which should have adequate antifreeze/water solution in it. While it should be inspected, tested and changed on occasion, I've never heard of winterizing that part of the system.

Chris

 

[Capt jgw]

On my raw water cooled engines, I've always removed the t-stat and put the cover back on before sucking the A/F through. And I use the green auto A/F, cheapest I can find on sale . The pink RV stuff gives no corrosion protection. I only use that in the potable water system.

 

[M-Captain]

Appreciate all the input here.

Chris, you are correct. Looking into it further, the thermostat only controls the closed cooling system on my "F" model. So no need to worry about it keeping the antifreeze out. The sea water only flows to the heat exchanger in my model and not to the engine as in the non-"F" models. So the method of sucking the antifreeze through the raw water intake should work fine. I'll leave the thermostat alone for now.

Thanks all!

Jim

 

[MitchM]

for 35 years here on lake erie most every diesel owner has winterized by pouring or sucking pink 50/50 35 - degrees- below - zero RV antifreeze into the raw water intake . (my yan mars 2 gm 20 F and 3 JH 4 E which is also "F" (F meaning it has radiator- style cooling plus raw water cooling ). we get - 20 degrees here. running the engine till 4 gallons have blown out the exhaust has worked fine to winterize .