Here is the fairly simple check list that I use. I will admit though that I do not do the RV anti-freeze flush part. I only do a thorough drain of the fresh water system.
WINTERIZING MADE SIMPLE Oct 2011
Aquire a Seloc or Clymer manual, or refer to your Merc Owner’s Manual.
-essentially you need to:
-hook up water to the outdrive using muffs, and warm up for 15 minutes or so at a fast idle, say 1500 rpms. Watch temps, oil pressure, and water flow out the exhaust ports on the transom assembly! Allow plenty of water flow. You should not see steam, and the risers should be no more than warm to the touch.
-Once warm (15-20 minutes), shut it off and get the oil draining ASAP while still warm (a quick drain makes this much easier).
-if the filter is top mounted, punch 2 or 3 holes in the top of it with a nail. This will help it drain back into the oilpan. After it has drained 10 minutes, quickly unscrew and replace with a new Merc filter. Tighten only ¾ turn by hand once seated.
-if the filter is bottom mounted, put a large baggie around it, loosen, quickly unscrew and drop in the baggie. Replace with new one.
-when the oil has drained completely, install the drain plug and refill with fresh 25W40 oil. Run for a short while to circulate the fresh oil; 5 minutes is good.
-check the oil filter and drain plug for any leakage.
-just before shutdown fog the cylinders with Storage Seal thru the carb or throttle.
-if FWC; drain seawater side of cooling system; exchanger and exhaust manifold drains, and any drains on the raw water inlet hose side.
-if RWC; MAKE SURE YOU GET EVERY WATER DRAIN PLUG OPENED AND DRAINED; ESPECIALLY THE BLOCK AND MANIFOLDS!
-optionally for added freeze protection, replace the drain plugs and pump pink RV anti-freeze thru the entire cooling system per instructions below.
-now drain and refill drive oil with Merc High Performance green. Refill from the bottom only using a pump, to the vent screw level. Top up the lube reservoir.
-grease all drive swivel fittings, steering fittings, gimbal fitting, and coupler fittings if possible.
-check all other fluids (drive lube, coolant, power steering, trim fluid) and top up as required.
-put some stabilizer in the gas
-park the boat and lower the drive
-remove the battery, or hook up trickle charger
-put the covers on
-grease the trailer bearings and check tire pressures
Follow this simple procedure for an optional anti-freeze flush.
First drain all water drains, as above, then reinstall all plugs.
Use a standard muff with a short cutoff length of garden hose (maybe 5 feet) stuck in a 5 gallon pail. Fill the pail with 3-4 gallons of pink AF and start her up.
The pump will quickly pull the AF thru the entire cooling system. Once you see it coming out the exhaust you are done. The bucket should be empty in a minute or two. Do not run the pump dry.
Obviously the muffs have to fully cover the water pickup holes in the drive leg to make this work. Use a little grease if in doubt.
Rod