Kohler 7.3 Cooling issue

[smcguckin27]

I had a somewhat interesting overheat problem on the Kohler Gen set in my 97 355. The raw water flow was cutting the ends off of the zincs and they found their way into the elbows where the raw water flows into the exhaust stream. I pulled the hoses and could see the obstructions in the elbows. I had to remove the elbows (easy) and push the jammed zincs back through the elbows to clear them.

Once I did that, I ensured I cut the zincs short and just checked them more often.

Of course I'm betting you don;t go through zincs like I did in the salt water, but if you have them in the HX, I'd check those elbows just to be sure you are getting full water flow.

Good Luck.

[650Guy]

that is interesting! Were you getting good water flow through the exhaust? or what you THOUGHT was good water flow?

[Helmsman]

I had the same problem with a 7.3 last year. It turned out to be a simple fix for me. The oil was a little low! It would run for fifteen or twenty minutes, then shut off. After getting the oil to the top mark, it ran just fine. Have also recently read of that “fix” elsewhere.

[Keith S]

The thermostat in that model has a flat disc that shuts off a passage when it opens. Removing the thermostat or modifying it will cause it to overheat. That model had an issue with getting airbound. A 1/8" pipe plug was added to the end of the exhaust manifold. Remove the plug and fill it until all the air is pushed out. Squeeze the hoses and force more out.

[650Guy]

Keith and SHarrisom that is great info! The oil thing may be something interesting as I have been holding off on changing the oil as I have not been able to run and heat it up consistently. I thought I had checked it in spring to verify qty but if it’s on the edge, maybe it’s kicking it off?

Here is my plan:

1). Install new thermostat
2). Refill coolant as it’s been drained as I was searching for thermostat parts in said engine. So with that in mind, I shall fill the coolant with cap off
3). Run gen and watch quantity filling as needed.
4). Once stable, shut engine down.
5). Install cap
6). Run engine again and bleed using bleed screw.
7). Shut down
8). Change oil
9). Start gen
10). Drink beer
11). Pray she stays running.

Anyone see any flaw in that process?

[Keith S]

The only thing i would add is get yourself an infrared heat gun. They are so cheap now, $30 at Harbor Freight, that there is no excuse not to have one. This would allow you to check the temp of the fresh water and the saltwater side of things. I would also consider moving #10 to #1.

[650Guy]

Great! Move #10, to 1 and add a heat gun, there is actually a harbor freight right by my marina. So that will be perfect.

[LES DOIT]

New to The forum and I need some help. 97 Carver 350 Mariner with 6.5 Kohler genset, it will run all day in the slip sitting still, handle any load you throw at it but cuts off after about 20 minutes of running on plane. I installed new impeller and seems like good water flow out the exhaust, strainer is clean. Took it to the marina for new bottom paint and they said some of the dome screen on the generator pickup was painted over which they corrected with the bottom job. I did inspect the generator pick up and it's all clear as well as they did a great job on the bottom paint.
Marina did some other work on the engines for me and when I pick the boat up first time on plane raw water hose blew off on port engine and it shut down. When it shut down it decelerated both engines and appeared the genset cut off to. If port engine shuts down will it shut off the genset at the same time? This just happened yesterday and the boat is back at the marina so I don't know if my generator issue is solved yet or not.

[Keith S]

You should probably have started a new thread since your problem is different than the original poster and your question could be lost. I once had a boat that instead of having a separate pickup for the gen used a T fitting off the main engine pickup. Underway the main engine fuel pump would overwhelm the generator fuel pump and the gen would shut down. I also have seen intake issues where the generator intake had a transducer or other thru-hull fitting in front of it and it would shut down from overheat on plane. I had one that had a scoop strainer installed backwards. The installer knew he could not install a forward facing scoop so he thought backwards would be OK. Ran fine at low speeds, but would overheat at high speed due to the funny water flow. So first verify your fuel system is independent, then use your infrared gun to check the generator exhaust temperature while underway.

[650Guy]

And it is SOLVED!!! Thank you all for the suggestions and help! I have now run the generator with A/C, TV, Hot Water heater running, and stereo jammen. Im pretty much guessing a complete thermostat was the end fix. I followed my steps above almost to the T, except after about 30-40 mins when the coolant had stabilized, the bubbles had stopped bubbling out the bleed hole, I had a nice Tito’s!

Again, Thank you all for the help and suggestions! The were key to me getting her up and running!!