Offshoreonly.com - freeze out plug locations

i finally got our little boat in the water after being held up by us moving and then by replacing the upper swivel shaft and steering lever. motor is a 454carb w a bravo 1.we went out last night (first ride!) and my wife notices steam coming out of engine compartment. i lift the hatch and the bilge is filling with water fast. i first assumed that i had a ripped or punctured bellows from repairing the steering . i headed for home , not wanting to sink.water kept rising,pump wouldnt keep up , so i shut it down and started bailing. long story short, police tow us in and boat stopped taking on water. when i crank the motor, she fires right up, but water is pouring out from rear of motor, just above or behind flywheel. my neighbor and i found a freeze (brass, not rubber)plug in bilge, so i know i popped one. question is how many are there? i have crusaders in my other boat, and no mention of the plugs in that manual. i dont have a merc manual. i'm guessing that there are plugs behind the flywheel. all the other visible plugs are there and apparently properly seated. i'm kinda miffed that a 20.00 plug is gonna cause me to pull the motor. i live in a cold winter climate, so i winterize well. i always drain the motor, and manually pour the antifreeze in. anyone else ever see this ?