Re: How do I winterize my Mercruiser 470?
Buy a manual and follow the steps suggested. This is one engine where all drain plugs and freeze protection information is important.
By all means be sure you drain the sea water in the manifolds, risers and heat exchanger. Make sure the antifreeze protection is better than your coldest temps.
The engine circulating water pump is behind the alternator on these engines unless you have a retro fitted alternator. Freeze protection should include corrosion resistance on these models. My last recollection was three drain plugs. The elbow (heat riser), the manifold and the exchanger. Check and replace zincs... they are important on this engine.
Just for info; the 470's have a WP corrosion/cavitation issue and once bad enough, water would seep/leak into the alternator. That's why some went to the alternator retrofit on the side of the motor and not integral. Zincs help to slow corrosion so don't pooh pooh replacing them.
Good luck!
