1. Run the engine until oil pressure drops to “normal” levels indicating that it (the oil not the water) has risen in temperature. Oil changes are best done before haul out as the engine can be properly warmed up and the oil is easier to pump out.
2. Shut down the engine.
Let it sit 5-10 minutes to let all the oil drain back down into the oil pan.
3. Remove the four bolts holding the transmission cover from the top of the transmission and GENTLY remove the cover taking great care with the cork gasket under it. I place this cover and bolts on a single piece of paper towel or cardboard on the counter.
4. Use a hand pump with a narrow tube pick up set into the oil in the transmission to vacuum up the oil into an empty four-liter container.
That is definitely
the Hard Way.
Spend $38 on this oil change kit
from Moyer Marine
. You can find it at the bottom of the Kits/Accessories page
. You'll get the same amount of oil out and won't ever have to disassemble anything.
Coupled with this Moeller fluid extraction kit
from West Marine (has a 5-star rating there, and for good reason, IMO):
Oil changes are a snap.
6. Replace the cover and the bolts.
And possibly the gasket.
7. Add approximately 3 liters of 10W 40 oil
Actually, the A-4 was designed for straight 30-weight oil. 10W30 is the next best thing.
9. Mix two liters of antifreeze with two liters of water and place in a four liter container,
I just put in straight purple RV antifreeze and have done with it.
10. Close the sea-**** and remove the hose from the intake. If the hose is short procure a 4–5 foot length of ½” or 5/8” heater hose and instead remove the hose from the water pump and hook up the new hose to it with a hose clamp. Insert the hose into the bottom of the bottle of antifreeze mix. Start the engine. While it is running look out the tailpipe for the color to come out. Shut down the engine.
To be clear: If the thermostat is not open, you will not be thoroughly flushing the entire engine block. And, at this time of the year in cold climates, it will take a while for it to open and it'll close-up relatively quickly.
Another way to do it, and the way it must be done on the hard, as you can't warm the engine up enough there, is to remove the thermostat, put the thermostat housing back on, and pinch off the bypass hose with a pair of vice grips. I'm going to do it that way this season.
11. Take a disposable plastic drinking cup and remove ¼ cup of antifreeze from the aft port drain plug.
I just went ahead and opened all three of them (the PO had replaced the plugs with valves), and let the RV anti-freeze drain into the bilge. Then I mopped that out.
22. Fill the fuel tank to within 1” of the top (not so easy to do) and add one cup of Methyl Hydrate to aid in the absorption of any water in the tank.
Stabil wouldn't be a bad idea, either.
24. Spray Mercury Marine Storage Seal (preferred) in the combustion chambers or add some (1/16 of a cup) of engine oil to the spark plug holes. Turn the engine over several turns by hand with the hand crank (or with the starter motor if a towel is placed upon the engine head to catch the splashing. This coats the valves and rings and cylinder walls with a protective film for rust prevention.
Everybody has a different way of doing this. Don Moyer recommends squirting Marvel Mystery Oil into the cylinders. The guy at the auto parts store that looked like he'd been wrenching on engines since before the A-4 was even created said to spray misting oil into the carb of the running engine until it stalled. This is what I did.
It looks like nobody mentioned the head and holding tank yet?
Close the water intake to the head. Dump a box of baking soda and some white vinegar into the toilet and pump it through. Some time later, pump-out the holding tank. Fill it up with fresh water and pump it out again, if you can. (Our club has a pump-out, so it's easy for us.) Dump a gallon of RV anti-freeze into the toilet and pump most of it through. Once the boat's on the hard, re-open the water intake to the head so it can drain.
To the OP: Your best resource for all things relating to your A-4 is unquestionably Moyer Marine