Something that is not in the books but very important especially on Fords, after draining the block, lower the front of the boat as low as possible to help drain the engine. A car/truck engine sits pretty level & this is not an issue for them, but in our boats the 12+ degree angle holds water in the back of the block unless tilted down to erase the 12 deg. On Fords the block drains are off-set, the port side is in the back of the block & is not an issue, but the starboard side is in the front of the block and will trap alot of water behind the drain. GM are centered in the block.
FYI just found some higher quality ALL BRASS drain plugs that can be used on the block drains, just replaced the plugs with drains on my Legend this afternoon, will put these on the Parts Web site monday.