quick winterizing question with closed cooling

I have an older I/O and am about to winterize it, it does have a closed cooling system. I was wondering if i need to run antifreeze through it still, i would think so since most of it is cooled with antifreeze....but want to make sure. Thanks

You can run anit freeze or just drain all the water out of it.
Since the closed cooling has antifreeze in the motor, you don't need to worry about the motor freezing. However, other parts of your cooling system can freeze and cause problems. So, you still need to get the water out of the rest of the cooling system.

On my boat, I had a drain plug in my cooling system - which is also where you replace the zinc.

In addition to that, there were the normal quick disconnect hoses and the hose going up to the cooling system which I had to disconnect to get all the water out of.

If this doesn't make sense, call the dealer and ask them what to do.

The guys at Bakes Marine in Seattle showed me how to do this stuff myself on my Malibu. Once they showed me, it was super easy.

If you do have a dealer do it, you should arrange to have them show you how they do it. That way, you would only have to pay once.