My boat has Kolher 5ecd generator and it keeps overheating. Things I have done to this point:

Cleaned the sea strainer
Changed the impeller (old one looked just fine)
Back flushed the heat exchange
Flushed the coolant and put new coolant in

It was still over heating. There is plenty of raw water running through the system and the heat exchanger stays cool but the manifold is getting very hot.

Finally I pulled out the thermostat and tried to run it without the thermostat and it's still over heating.

At this point I'm thinking it might be the coolant pump but I can't find anything in the manual on replacing this. Has anyone been through this? Is there something that I missed? I know for sure it is overheating and it is not just a sensor. I have a call into the Kohler Mechanic in Destin but I figured it was worth a shot to ask on here.

Thanks,
Aaron

What is it doing when it overheats? How long does it take to overheat? Does it start/run fine until then?

Starts and runs fine... Takes maybe 5 minutes from the time it is cold to get hot.. It then shuts down and give me a "HE" code (over heat). I know the fluid is getting hot because it starts to steam and boil over into the overflow. I'm told there is a way to bleed the system so I'm going to try that next. I'm also told that getting to the Coolant pump is a major pain in the ass.

Had the same problem with a 7 series kohler , was a real head scratcher. Ended up having a air pocket in the system. If you have acess to one of those radiator style funnel with the adapters put that on first, and open the bleed in the u hose. At the top .

Definitely have air in the coolant system. I had a 7.3 that I ran around for a couple yrs trying to figure it out. I had small screw/plug on the top of the heat exchanger that was the bleeder or air escape for the coolant system. I would take a syringe and put coolant into this hole until the coolant flowed over the top. Then put the plug back in. I would still have problems time to time. Then I realized one more thing. When the boat sat in the water, it would sit nose up higher than the back. This would essentially make the generator sit in the boat higher in the front than in the back. My generator sat behind my bench seat cross ways in the engine compartment. I realized that if you grab the back side of the generator and pull on it toward the front, the rubber mounts would allow the generator to be more level. I would repeat the filling process over again. This fixed my problem. There cant be any air bubble in there or it will over heat.

^^^ agreed. Purge air out of the system. Fought it before on my 5E

Good info guys, I really hope its not the coolant pump. I'll get back to the boat sometime this week to give that a try, and report back.
thanks,
Aaron

Air bound . There is a service bulletin. Remove 1/8 pipe plug and purge keep filling w antifreeze . For some reason tiny air bubbles get trapped at the heat exchanger and mine did the same thing . 5.0 kohler. Boat was 2001 w 200 hrs gen only had under 20 hrs since new and then we figured out why after changing everything.
Frustrating.

Final got back to boat yesterday and topped off the coolant through the vent like was suggested and the generator ran great all day, no overheating issues.
Thanks guys!
Aaron

I love happy endings!