I just replaced the water
pump on my Kohler 8 kw genset. It was leaking at the pump. I put it on and got no water
flow. Felt the plate and of course it was getting hot and thats when I shut it down. Burned up a impeller like you did a few years ago leaving the seacock shut. I ALWAYS look for water expelling with exhaust
and I always feel the plate on sea water pump now. Anyway new pump installed no water flow. I check for water to the strainer. Water coming in and so I was baffled. I took off the hose and primed it by pouring water down the hose and then reattaching. I then turned it on and ran to outside of boat noticing water spitting a little outside the boat. I then turned it off. I turned it back on and more water spitting. I felt the face plate on the sea water pump and it was cool. I did not like the amount of water flow but as I waited it increased a little at a time. I judge the temperature by feeling the plate. If hot turn it off immedately, if warm I wait and let is cool. When genset is turned off then the plate is quite warm as genset is warm... Hope this helps.
Question where is the easiest place on your Kohler to drain the anti-freeze. Mine is in very very tight quarters and very hard to do anything with it. Changing the water pump was a job. I also had a bad belt that I changed and left off the shroud
so I could examine the belt and tension more effectively.