Semantics
I was a little confused with your last post but I think I'm coming around now. I think I see a little confusion about which water is which. Sea water and raw water are the same. Fresh water and internal water are the same. The raw water is pumped in, goes through one side of the heat exchanger and is then dumped overboard through the exhaust. The fresh water stays in the engine. It is circulated through the engine where it gets hot, it then goes through the other side of the heat exchanger where it is cooled, only to go back through the block. When you change the antifreeze solution (fresh or internal water), you open the drains on the block and manifold. These usually are the ones with the plastic tubes. The antifreeze is usually colored. If you open a petcock and a colored liquid comes out, it's probably one that you are looking for. You will also have the fresh water going to your water heater and returning. You can drain these tubes by blowing in one and allowing the other to drain. A Wet Vac is also great. Wrap a rag around one of the hoses and stick it into the vacuum hose. I hope this gives an answer to your question.
