Does your boat have catalytic converters?
On mine, there wasn't an easy way to draw antifreeze directly into the water pump. I used a fake-a-lake. You do need to drain all the water first, and reconnect all the hoses and plugs. https://uploads.tapatalk-cdn.com/201...9e3f303280.jpg
I suppose I will be fogging the cylinders directly though at some point. Maybe tomorrow if it's not raining. https://uploads.tapatalk-cdn.com/201...654eeb2918.jpg