I have the YSE12 here ...
Today I ran it with the intake hose in a bucket, said bucket being refilled by a water hose from the house. After 15 minutes or so, I figured the oil
was mixed up and warm enough for the oil change
so turned off the house supply water and ran out the water in the bucket. Then I went another 10 seconds to discharge a bit of water from the system, and then poured in 2 gallons of antifreeze into the bucket. I stopped the engine when the antifreeze ran out.
I would have followed the directions in my manual which involved the drain cock, and the manual cranking lever but there are issues: my drain cock doesn't ever drain any water, so it must be plugged somehow, and I don't have the chain that connects the manual crank spindle to the accessory output shaft. I still intend to disconnect hoses and take the water pump off to drain what I can. Plus I think the antifreeze sometimes damages impellers. Might even disconnect the exhaust
Hopefully I have done and will do enough, as the old beast works pretty well and don't want to lose her.
Anyhow, even if the antifreeze is diluted too much, it should at least buy me another month to sort things out better. It is going down to low 20s in a few nights, so I had to do something sooner rather than later even if it isn't entirely robust yet.