Flushing the Engine Coolant (every 2 yrs) - Ken Johnson "WindSong"

The Volvo owners manual that came with the boat says drain & replace the coolant every 2 years (if you're using std ethylene glycol / H2O coolant). WindSong is a 2003 boat, so - it's time.

Following a recommendation from Bruce Mundle at Bavaria Yachts USA and Tom Vandenberg (Spiced Rhumb) I removed the bottom step mounting board to improve access to the engine - this is a good idea, it helps with access to the bilges for getting the spent coolant out. Also, since I get some clogging in the fitting for the overflow tank atop the heat exchanger (have since new), it was determined that I should flush the engine with dilute radiator flush (Volvo-Penta dealer). So, here's what I did:

1. Clean the engine bilge as much as possible - remove any absorbant materials from under the engine.

2. Run the engine until warm to circulate all the coolant. Drain all the coolant by removing the drain plug located just in front of the oil filter on the MD2030. It's easy to identify the drain plug - it's square, rather than hex, and it is a pipe fitting plug, not bottomed into the engine. The coolant all drains into the engine bilge where it is held by the geometry of the bilge (doesn't get into the main hull bilge). Approx 1-1/2 gal (5 liters) of coolant). Remove and dispose. I used a small wet-dry vac to get all the coolant out of the bilge, poured it into gallon containers and carted it to a disposal facility at the marina.

3. Mix a dilute solution of radiator flush - I used about 4 oz in a gallon of clean water. Replace the drain plug, putting a few wraps of teflon tape on the threads. Fill the engine with that (including an inch or so in the overflow tank). Run the engine for a few minutes to circulate. Drain again, as above.

4. On WindSong, the flush was dirty - so I repeated step 3 with another mix of flush and water - same dilution, and drained again.

5. Fill with plain tap water and repeat the flush process. On WindSong, the drain was pretty clear at this point, so I did not repeat this step.

6. Run a few gallons of fresh water through the engine by pouring it into the cap on the heat exchanger while the engine drain plug is still out (following the last drain). Do not run the engine in this configuration. Again, on WindSong, this was pretty clear so I knew the engine was clean, and the flush solution was out.

7. Mix anti-freeze and water 50 / 50 and fill the engine and overflow tank - I used the extended life, all metals, red-stuff, instead of the standard auto antifreeze. Run the engine for a few minutes and then keep filling the overflow tank until the engine doesn't take any more. Will probably have to repeat this later to be certain it's full. It took a little over 1 gallon of coolant to re-fill this way, so it may be about 1/2 liter low. Add new absorbant to the bilge after it's dry.

9. Done! But check the coolant level each time you run the engine for a few cycles - it may drink a little more out of the overflow tank.