Balmar regulator and 50 hp diesel

Yesterday was the first test launch for our new charging system. We tested the system before launch and got 40 amps at idle and 110 amps at 2000 rpm. That's more than I expected from our 120 amp alternator, even when the engine was not up to operating temp. At the launch ramp things did not go well. After the test, I had enclosed all the wires in split conduit and zip tied them to make everything neat and tidy. At launch we got zero amps. I was sure I had pulled something loose, so we motored to our dock to find the problem. No tack, oil pressure or temp gauge, but everything was ok when we tested on the hard, so we ran the one hour. I had to wait till the engine cooled to find the problem because I had to lay on the engine to reach the wires. Found the problem and had everything working a few hours later. We took the boat out, wanting to run for a few hours to charge the batteries. Idled at the dock for 10 minutes and got 10 minutes from the dock when the engine overheated.
By the time we got back it was too late to do anything, but I am going back today. When we restarted the engine after cool down I noticed that there was almost no water coming out of the exhaust. Maybe I picked up a plastic bag. Maybe the impeller melted when we overheated. Maybe we over heated because the engine is working too hard to put out 110 amps. I think of a 50 hp diesel as a strong power source. This is, after all, a Kabota tractor engine, But maybe I need to back off the alternator with the belt load managing setting. I did set it at 1, just in case. I hate to give up all that charging potential, but the overheating form overworking theory seems likely. Ill know more tomorrow.

An alternator rated at 120 amps will not last long while putting out 110 amps continuously even a high output Balmar. Check the alternator’s case temp while it’s running in that condition. I bet it is above 225 degrees, the maximum recommended.

You have a Balmar regulator, right. Install the alternator temp probe and it will back off the current to keep the alternator temp reasonable.

And FWIW a 110 amp alternator load on a 50 hp engine isn’t going to overload and overheat the engine. Maybe 5 hp at most to drive the alternator. And in any case even full load on the engine should not cause it to overheat. Sounds like you have a cooling problem.

David

[QUOTE="REO, post: 1242149, member: 12374. When we restarted the engine after cool down I noticed that there was almost no water coming out of the exhaust. Maybe I picked up a plastic bag. Maybe the impeller melted when we overheated. Maybe we over heated because the engine is working too hard to put out 110 amps. I think of a 50 hp diesel as a strong power source. This is, after all, a Kabota tractor engine, But maybe I need to back off the alternator with the belt load managing setting. I did set it at 1, just in case. I hate to give up all that charging potential, but the overheating form overworking theory seems likely. I’ll know more tomorrow.
[/QUOTE]

With few available details and from this distance away I would think that your overheat experience is a result of “almost no water coming out the exhaust”, not the combined propulsion and alternator heat load exceeding the engine’s maximum cooling capacity.

A 12V alternator producing 120 A is equal to be about 2 HP. Now add for the fact that the alternator itself is likely only 60% efficient, plus belt losses and the load on the 50 HP (at rated PRM only) Kubota would not exceed 4 HP.

Don’t think that caused things to boil.

You would be wise to service your cooling (both raw water and coolant) systems.

Perhaps the belt is slipping, reducing the water pump speed and flow?

Check the strainer, then check the impeller. If still poor water flow then send a diver down.

I checked the impeller. No problem. I removed the hose from the impeller output. good water flow. I removed the hose at the exhaust system water injection point. good watered flow through the heat exchanger. I checked the muffler. no apparent damage. I don't know why I felt that the water flow sounds different, but there is clearly good water flow through the sea water side of the cooling system. I started the engine and ran it under light load at the dock. Started to overheat after 15 minutes. I already have the temperature probes and the alternator was continuing to put out about 50 amps when the engine overheated. This engine has about 15 hours and two years on it. I guess I'll look at the heat exchanger next.

Get some temp readings along the raw water path. Make sure it’s warming up as it goes through each device.
It also may be possible you have a stuck thermostat on the fresh water side, or some other blockage like water heater coil or something.

Here is another theory. This boat has been extensively modified since it was last in the water. I added lots of weight. 2 -300 ah batteries. a 2000 watt inverter more than a hundred feet of 2-0 cable, a reserve 15 gallon water tank and a bit of cabinetry.
It's hidden under the swim platform, but I think the stern may be down enough to put the exhaust partially under water. Could that back pressure cause the change in sound and maybe reduced flow of sea water. The water lift muffler had a distinct burst of water flow when the muffler built up pressure to expel the cooling water. Now it just doesn't have that much of a burst of pressure sound. But if that's the problem, why didn't it overheat during the first one hour trip from the launch site to our dock?

Hard to say. With the exhaust partially buried it’s hard to tell if the water is really coming out like it should, I wonder if there’s blockage at the elbow?
In any case, getting some temp readings at various places will help identify where the problem is.
Incoming hose temp, water pump temp, after the heat exchanger temp. You get the idea. Real numbers lead to real answers.

In my Kubota 2203 which likely is about 40 HP as it powers a 20 kW alternator, the coolant drops about 50 F. (150 to 100 F.) when run through the raw water (@ 60 F.) cooled heat exchanger.

Try using your IR Thermometer on yours and see what you get.