I recently changed my impellar on my Kohler 10 EOZD genset with Yanmar engine. I also changed the coolant hoses and cleaned out heat exchanger. I ended up with an overheat auto shut down after 7 minutes. After much internet surfing I decided to try burbing air bubble out of coolant side. I had use the boat previous day without genset and when I removed coolant cap today the coolant level had gone down signifigantly. I topped it off and proceeded to run engine for an hour with out overheat shutdown. I presume the planing and wave action broke coolant bubble free saving me try to get the plug out of top of coolant resevoir which was not coming loose without a lot of effort!