Re: 4hp Yahama cooling issue
Obviously don't run it long after noticing a lack of cooling water. You will damage the engine.
Check to see if the thermostat is blocked with sand and other grit. I found a similar thing with my small outboard. I opened up the thermostat, cleaned it out and briefly let it run with it open. Out came a lot of junk and now cools normally.
The impeller would be the next item to check.
