Don't take a chance - use the antifreeze! It takes about 40 Gal to do our 53 - just bite the bullet and do it!. A year or two ago Dr Jim (Rosenthal) used compressed air to winterize and ended up with a ruptured water line. He posted on that a while back. I had been thinking about using compressed air instead of AF but his post convinced me NOT to do it.
It just so happens that a friend in Stamford just bought a 53 and asked me for some FW winterizing info. Yesterday I emailed him and what follows is the text of what I sent him. Perhaps it will help:
As usual, took 40Gal of antifreeze for winterizing. I tried to get by with 6 cases - 36 gal but I needed to buy another case to finish it off! First I drain the water heater by turning the valves on top so that water can't be pumped into it and will bypass it - there should be 3 valves on the tank lines. One valve lets cold water in, one lets hot water out, and the third allows the water from the pump to bypass the tank completely. I turn the in/outs "off" and the bypass to open (it's normally closed) Then I release the overflow valve on the heater and open the drain fitting on the bottom through a hose and directly to the seachest and overboard. That will take quite a while just let it drain and move to other things.
Then drain all the water out of the water tank(s) by running the taps. (This can be going on at the same time the water heater is draining.) Then, when the pump can't pull any more water, I shut off the pump and the valve in the line from the tank to the pump. Our boat has a series of valves in the system that allows me to isolate the section from the pump forward and from the pump back. there are also two additional vlaves that allow a hose to be attached to the system. Then I fill a 5 gal bucket with antifreeze, connect the hose to the pump intake side and drop the other end in the bucket. Let the system pressurize again and simply turn on the taps in succesion until the pink stuff comes out - checking to keep sufficient a-freeze in the bucket.
Once the water heater has drained, close the drain valve and open the water input valve to the heater. Close the "popoff" valve that you opened to allow the water to drain. Close the bypass valve. Antifreeze from the bucket/pump will now start flowing into the water heater. Open the drain valve and, when pink stuff shows up - it should quite quickly - you can close the water heater drain valve. You're done with this part!
If you winterized the engine's RW side when you changed the oil by connecting a bucket of antifreeze to the seacock or intake hose - your've already taken care of the following. If not:
When that's done, I close the engine RW intake seacock, remove the Zinc plug on the front of the engine overflow tank. This plug is in the RAW Water side of the system. A regular garden hose fitting can screw into it. Connect a water hose from the engine room fresh water connection to the engine. Fill your antifreeze bucket again and, adding a-freeze as needed, run 8-10 gal of a-freeze into the engine RW system. This will ensure enough gets into the exhaust and muffler to prevent any freezing problems. Do this on both engines. Leaving the seacock valve closed, open the top of the seacock and ensure there is some antifreeze in there. If not, pour a little in - doesn't need much.
The genny will also have a fitting on the RW side somewhere that may or may not take a garden hose fitting - you may have to find a proper sized hose fitting. Close the seacock, attach the engine room hose and run a couple of gallons into the system. Same thing - if there's none in the seacock, pour a little in.
Make sure you allow the fridge/icemaker to run so antifreeze can get into those lines as well. I leave the water system pressurized with the antifreeze bucket in place overnight. Then, the next day you can release all the pressure and switch off the water pump. Pour 4-5 gallons of afreeze into the Fresh water tank OR, using the same set up you did for everything else, if you have a valve system that allows you to isolate the tank feed AND connect a hose to it, you can simply pump antifreeze backwards into the tank..
If you have the standard Galley Maid Raw Water heads (I don't remember if you do or not) close the INTAKE seacock for all of them. Pour 2 gallons of afreeze into each head and flush it until there is nothing standing in the bowl. Pour in another gallon and do it again. The seacock tops should be opened and some afreeze poured in or they can be left open. If you have valves on the seacock that allow you to connect a hose, you can hook that up and flush the toilet normally which will pull the antifreeze in and you won't have to worry about adding any to the seacock basket.
. I use 18 galllons total on my 43. I run 6 gallon through each engine. I use a bucket and I place the the hose off the strainer into a bucket. I drain the hot water tank and add a by pass line. While that drains I take the fresh water hose off of the head input and pump a 1/2 gallon in each the head (2). I pump the fresh water tank till empty. I add 2 gallon of a/f to the fresh water holding tank. Charge the system with the boat water pump until I have a/f to the first faucet. I shut off the pump. I then add a small 110 volt pump to the city water input. I then charge the lines with a/f. and systematically turn on the faucet furthest from the supply until I get a/f. I then do the rest of the faucets the same way. During this time I leave the ice maker on until I get pink in the tray and I'm done. I have never had a line on the boat freeze up. I would NEVER ,NEVER blow air or vacuum a boat dry. I have done this to a cottage for 50 years and we still have the occasional busted line. You can never get all the water out in the short time you have air on the lines. You can not have enough air volume to blow all the water from the lines. The air will blow through the water leaving a small amount behind to gather and puddle some place. That has been my experience. But I'm not always correct. 
