I don't think it works like that since the area surrounding that plug is open air that can go below freezing. I would try to figure out how to drain it.

 

Do you expect temps to stay low enough, for long enough, that a simple bilge heater wouldn't safice?

 

My boat is on Lake Lanier. I don't drain anything. I put a bilge heater in and have not had a problem (except a few years ago when an ice storm knocked out power and I ended up spending the night on the boat to run the engine every few hours to keep it from freezing in -6 degrees with the wind chill).

 

I'm not a fan of leaving things dry as it can lead to rust/corrosion on the inside and antifreeze is cheap (relatively speaking). Whether or not you'd be safe... I can't comment on that as I don't have experience in your neck of the woods - we're in a "must winterize" climate :smt001

But, to answer your question... I assume you're referring to the fuel cooler behind the port-side engine mount. It's certainly not the easiest to reach, but with the right angle of attack, removing of certain items on the shelf and the proper tools, it can be done. Having a single engine in the compartment makes it a little easier than if it was twins, too. If it's just not going to happen for you, then you can also remove the rubber hose on either side of the cooler. Still another way is to remove the hose at the t-stat housing and push that (removed) end down to the bottom of the bilge to drain it that way. You might kink the hose in the process, so move it around to make nothing is trapped by the kink.

Questions (again, because I'm from a colder area)... what about the raw water pump side? Did you remove the output hose for draining (and input, then bump the engine over a few times to evacuate water from the pump)? Do you get a siphoning effect of outside water being drawn in? Will you need to take the raw water input hose and plug/fasten it higher than the water level?