Yes. This is my winterizing procedure relative to my 2008 100hp Yanmar:
1. Replace primary and secondary fuel filters and impeller as needed.
2. Run the engine for 30 minutes adding water to the strainer with a garden hose in order to verify operation after replacing filters and to warm it up.
3. Change oil and filter by sucking oil out through the dipstick using a vacuum type oil changer.
4. Drain the muffler by removing plastic cap at bottom of muffler. Replace cap.
5. Add antifreeze to strainer while starting engine (must act quickly to keep up with the flow - takes two people). Takes about 3.5 gal of antifreeze to see red coming out of exhaust.
6. You can drain the muffler again if you like, but I leave the antifreeze in the muffler.
Hope that helps
