After reading this thread and the one the link leads to, it sounds all so complicated with extra hoses and tee's and valves, etc.
I have a very (very) large sea strainer and just close the thru hull
, take the top off the strainer and stick a garden hose in it and run the engine to warm it up, then start dumping in anti-freeze (3 opened gallon bottles of pink stuff pre-positioned so I can grab them quickly) as I shut off the flow through the garden hose. It's tough to predict just how much water to pump in so to make sure there's enough I usually end up with a fair amount of fresh water overflowing into the bilge
and some anti-freeze too, but that's OK. When it's all pink coming out of the exhaust, it's time to shut down the engine and stop dumping in the pink stuff. The last step is to screw the top back on the strainer and open the thru hull
so the salt water
remaining in the intake hose up to the height of the waterline can drain out, and I'm ready to go in the spring.
My last boat had a much smaller sea strainer (held less than a quart of water and had a clear plastic top with a wing nut holding it on) and I used pretty much the same method to winterize that engine. The only difference being that I had to hold the garden hose over the strainer rather than sticking the end in. But in either case, I've never felt the need for any extra valves or hoses. I waste some pink antifreeze due to spillage but it seems worth it to spend an extra $5 or $10 each fall to keep things super simple and not have to take any hoses off the thru hull
or add T's that only get used once a year.