Merc I/o Winterize issue

[Iggy]

Personal, I would not drain an open system. By leaving the AF in, you not putting air into the system. Air will cause rust to form.
But thats me......

 

[cjm13905]

So had someone do the winterize this year and he showed me where the 6th plug was.
If you are facing the engine, it is back under the front right engine mount. Very hard to see and get to.
You would think the engineers would design better, but what do they care.