Draining closed cooling system

[Toughship]

Have 7.4 Crusaders and want to replace the coolant in the closed cooling system and was wondering if the old coolant can be removed with a shop vacuum?
   Prefer to follow the manual and open the appropriate drain plugs but I cannot reach all of them , plus the boat is in the water and don’t want to drain the old antifreeze into the bilge.

[TiaraTom]

I just did exactly this. Could not/did not access anything unreachable like outer drain plug and hoses. I followed the instructions in the manual otherwise. In some cases I was able to catch with a small bucket. In other cases I was able to feed right into running wet shop vac. The rest drained into bilge. I then wet shop vac'ed that. Hosed everything down afterwards and shop vac'ed that too. All into 5 gallon buckets with lids.