Originally Posted by Alex W
A fresh water cooled marine engine still draws in raw water. The raw water goes through a heat exchanger which cools down the engine cooling water.
This way the salt water is only in one small system instead of being pumped through the whole engine.
Thanks. I would assume there is a separate pump for the raw water. However, the only drawing I've been able to find for the engine shows a single cooling water pump. Unfortunately, the only Yanmar document the previous owner had is a six-page user's manual that is very light on any details.