The Power Steering Cooler is generally located on the port side next to the Oil Pan on Alpha drive equipped boats. The older ones required you to remove one hose to drain them. The newer ones have a blue drain plug at the rear / bottom.

There is no winterization needed for a selectable exhaust system. When you drain the Exhaust Manifolds, you've done all you need there.

Just did it on my 502. Ran the engine until it was up to temp, then switched to antifreeze. Did not drain the blocks since I didn't want the engine cooling down again. Got about 3 gallons in there and it started coming out the exhaust so I shut it down. Checked the block by removing the drain plug and took a sample. It was pink :-)

This is what I do. Have always pulled the T stats. I feel better this way. Mostly because running off of house garden hose it takes for ever t ogetto temp. And usually I do it when its 50 outside and it really never does get to temp.
I have tried using the hot water tap, but that just depleats the hotwater tank to fast

Thermos out, back together and run. Never had an issue
i usually run 6-7 gallons of anti freeze thru each motor to be certain.

Other thing this does, is keeps the thermo housing free of crud. First year, a few years of not doing it this way, and the thermostat was a pain to get out. Had to break apart the white spacer on both to get them out. Since then they come out easy.

Like others have said, you leave this all winter you better plan on new motors.
If your truly lucky you might just end up with the freeze plugs blown out, but that is one hell of a gamble!

Unless your in a heated buidling!

Depending on the yaer of the motor, you might need to be looking for brass plugs and not the newer Merc Blue plugs.

I actually go a couple steps further since I know the waters I boat in are muddy and sandy.
When first running on the water hose I pull the plugs with the water running and make sure all the plugs have strong streams of water out of them. Been a few times that I have to use a hanger to free up. Once you do this you will understand how much water really does push out the plugs when running Thus learn when doing it again what a partially plugges passage is like not pushing such a hard stream.

I am lucky enough to do this with my setup, I realize with Twin V hull it might be more difficult. But you could still shut the motor off, pull a plug with the hose running, and then start up for a bit to 'clean' it out

Pretty much the same here. But I run it on the hose (with hot water) to warm the engine and oil up, then change the oil & filter. Then pull the t-stat and put the housing only back on. Drain block and hoses then a large tub goes under the outdrive with +,-8 gal. of anti freeze, pump in tub with hose to ears on the OD. 4 inch PVC going from exhaust tips down to tub, plug in pump and start engine, then let it run for several minutes to circulate the antifreeze. Yeah, I know.... OVERKILL !!.... but that's just me. Then let the OD fluid drain for a couple days or so, and fill with new.

Not overkill when protecting blocks!

Draining the engine of water before anti freeze is a must. If you don't, you start mixing water with antifreeze, degrading the freeze properties severely. -50F turns into 0F antifreeze with very little water.

Thanks for the advice guys your all right never want to take The easy way out so I'm looking again and iv found what almost looks like a small transom plug toward the bottom of the block and in the middle would this be it? The blocks are 1990s

Mercury used several styles of block plugs over the years. There were 7/16" brass hex head plugs, brass t-head plugs and the newest ones are blue plastic. Sounds like you have the first one I mentioned. Should be one on each side of the block. And not to harp on it, but stick something in the hole after you pull the plug to make sure sediment didn't clog the drain. You should get a nice, smooth flow of water when it's clear.