Re: Cracked block from freezing?
I did try rigging up a livewell pump to the winterizing tank for that very purpose, keep in mind that the muffs have to fit tight for it to work. Realizing how much easier and safer manually backfilling is, I wound up using my contraption as a flusher for my drum brakes where there is not a hose at the ramp. Plug it into the trailer plug on the Jeep and it works well.
When you put the boat in the water, the static water pressure because of how the boat sits in the water, forces water from the drive intakes all the way into the raw water hose from the transom. Then an engine mounted impeller can prime without difficulty. When you do this with the winterizing tank, gravity feed may not be adequate to raise the water level up the foot and a half or so it must travel from the drive intakes to fill that hose. Pump pressure may work, if it does not suck air around the muffs.
If you have a Bravo or Volvo (engine mounted impeller) I'd say forget even trying this. Just do it the way I described (manual backfill). If you an Alpha with the impeller in the lower unit it can work because the pump is pushing from right above the intakes, not sucking from 4 feet away on the front of the engine.
Just as an engineering aside, I have a Cobra which has the impeller in the upper gear housing. When you have a cooling problem one of these, one of the checks you do is to see if water is getting to the water passage in the impeller mount. To make water squirt out of this passage the muffs must fit TIGHT, if not water does not even make it that far. So that's why I say, be careful if you want to pump in AF with an engine mounted impeller....