Something else to consider, with that Alpha 1 outdrive, a tight fitting impeller can prevent water from draining from the pathway from the pump up to the motor.

 

Turns out the downside of trusting the single point system is that the little tubes from the block to the drainage collector can become blocked over time. .

Correct, that is exactly what we had discussed with you in your other post\ - that they can get clogged up. However, assuming that regular use will keep that from happening is not guaranteed. It certainly helps, but it doesn't solve the problem. There is no way to know if one of them is getting clogged without removing them. They're actually pretty easy to remove from the engine side and the WDM side - it's just that you'd be doing it by feel only... which is par for the course when working on boats.

But keep in mind that without pouring AF into the t-stat hoses, and pushing the remaining, standing water out, you still run the risk of water freezing and cracking the block if the temps drop low enough for long enough.

 

Thank you. I am going off to worry about the several degrees it may warm in the next hundred years or why logging's effects on birds outweighs the utility of harvesting the flammable trees. Meanwhile, here is a learned discussion of the weep holes that may or may not be in outdrives. https://www.thehulltruth.com/boating-forum/1016352-calling-all-mercruiser-geniuses.html

 

Winterizing and freeze proofing are versions of each other.
If you stick an air compressor blower nozzle into the drain hole where the blue plug comes out, you can hear air circulating throughout the entire cooling system, and know if anything is plugged.