Re: 2012 Mercury 3.0 TKS Thermostat
Introducing Antifreeze thru the water intakes is a really inefficient way to winterize an I/O. It also has great potential to do such a poor job that the block can easily crack, due to residual water. The best way is to drain the block of water, introduce antifreeze to the block via the recirculation hose (on the block water pump) until you see it drain, and then install the drain plugs and fill the block. Do the same with the manifold. It will take about 3 -4 gal of straight antifreeze to do it. You can drain, capture and reuse the antifreeze next winter. I urge you to read the I/O forum post on this matter. Alternatively, rebuilt motor longblocks are only a couple of grand, not including installation, if you crack your motor.
