I use my boat for walleye fishing when the temperatures go well below freezing. My concern is water left in the lower unit or block freezing and causing damage. Is there a product I could use to flush the lower unit after use such as an RV antifreeze? My thought is to displace the water with a solution using muffs. I have seen a product (biodegradeable)for winterizing a boat at the dock, but I contacted the manufacturer with questions and they don't respond.