Have you checked the water pump impeller?

 

When its running up to the point it shuts down, I have watched the water temp, oil pressure and volts. All are good.

 

The impeller could still be bad causing high exhaust temp leading to the exhaust temp switch the shut the generator down.

 

This is the most likely issue. Either the pickup/strainer is clogged or there is a problem with the pump. The temp gauge you are looking at is for the engine not the exhaust water temperature. All it takes is for water flow to be off by 30-40% for the exhaust manifold to start heating up (engine temp will look normal). My guess is that if you point an infrared temp gun at the exhaust manifold.....you can watch it happening. The trip point should be around 230 degrees.

 

We are fighting pretty much the same issue with ours. Same gennie. So far we have replaced a fuel line that was cracked along the port stringer, just before the Racor filter. That seemed to make adifference for a while. Ours will run for hours sometime and 30 minutes others. Ours seems to restart and run fine after the 2nd start.

 

I am not familiar with the 12.5 gennie, but I am familiar with this same problem. Last season (2017) my generator began to act weird. Sometimes it would run for an hour or two with no problems, then would seem to randomly shut down. As the season progressed, the run times became shorter. During last winter's layup, I replaced cap, rotor, plugs, wires, oil filter and oil, and impeller. I also removed the heat exchanger and cleaned it as well. Assured that all was good, the spring of 2018 came an no improvement. Actually, it got worse. Gen would run for 20 minutes on first start up and then die. It would re-start immediately after quitting and I would go through this cycle as many times as I cared to do it. I also checked every sensor and anything else in my service manual. Late in the summer, after posting here, a fellow CSR member suggested checking the oil level in my governor. I had no idea there was oil in there or how in the world it worked. Did some research to find the appropriate amount of oil needed and dove in on a rainy Saturday. Sure enough, only about half the amount (3 oz) of oil needed was present in the governor. Drained the old out, replaced with exactly the correct amount, reinstalled and SUCCESS! Fired the generator and let it run at the dock for 4+ hours without a hiccup. This is a very easy procedure and should be covered in your manual. Check it out.

 

Thanks for getting back to me. You are talking about oil in the engine part of the genset, not the armature???

 

G, MckyD has a diesel genny, so a solenoid acts as the governor.

 

I believe the diesel generator still has a mechanical governor to regulate rpms. It would have a solenoid to shut off the fuel flow to shut down the generator. The oil gdavis is referring to is the oil in the mechanical governor. If it is too low it can't function properly. There is no oil in the armature end of the generator.

 

MckyD. You seem to be ignoring some of the advice given above. PlayDate is an ASE Certified mechanic and suggested that high exhaust temp caused by low water flow is the most likely cause. Just because you have water flow out the exhaust doesn't mean you have adequate water flow to keep the generator from shutting down. I agree with PlayDate, get an inexpensive infrared temp gun and check the exhaust manifold temp as the generator warms up. Second in line would be a problem with the governor. I'm not familiar with the system but if the governor malfunctions and allows the engine to overspeed then it may cause the fuel solenoid to shut off stopping the generator.

 

HI, Thanks for the reply. If you check my previous posts you will see that I have used a infrared temp gun to determine that the temps across the engine, manifolds are consistent with that showing on the temp gauge. I have also accessed the flow rate of the raw water and as a precaution replaced the impeller. Again as per my previous posts. I have also checked the speed to ensure that it is running at the correct speed to give me the correct hertz.

 

I went back over your posts and this is the first mention of an infrared thermometer. Checking all over the engine with the IR thermometer and having it agree with your analog temp gauge is fine but did you check the temp at the exhaust manifold/hose where the exhaust temp shutdown sensor is located? You can have enough water flow to cool the engine but that may not be enough to keep the exhaust system from overheating. Will the generator shut down more quickly when under heavy load than under no load. If so it would point even more to an overheat shutdown.

 

Still following, looking for more ideas. Thanks

 

I'm still not convinced you don't have a water flow problem.

Why? Because the symptoms you describe are identical to a safety tripping. Runs for a while.....shuts down....will only run with the pre-heat held down. If, after 20 minutes it restarts and runs without holding the pre-heat switch......it is related to the safeties. The pre-heat bypasses the safeties to energize the fuel pump. Of the safeties.....the most likely candidate is the exhaust water temperature safety since you can monitor the oil pressure and engine temperature on your gauges which makes troubleshooting a lot easier.

A governor problem behaves differently. First, it doesn't care about the pre-heat switch on a restart. Second, you can hear it surging.

I don't know the history of your boat's generator but given the symptoms and restart behavior....my money is on a water flow problem. It can be:

-A clogged raw water intake
-A clogged strainer
-A clogged heat exchanger
-A bad impeller
-A badly scored pump
-A bad sensor

As hottoddie said....having water flow is not enough. It has to be enough to cool the heat exchanger and exhaust. It is probably something that you have already looked and thought was okay. It's okay to look for more suggestions but with only four safeties and the behavior of a safety shutdown......that's where I would focus.

BTW the green light shows the normal status of the control board. It too is behaving on a quick restart as a safety has been tripped.

 

Ok, I am at the boat again today, however the question is what part does the alternator play in all this? The circuit runs through the safety switches, fuel solenoid and lift pump before ending up at the alternator and connected to the R on the back of the alternator. There is another wire connected to the L terminal on the back that also runs back through the same circuit. My thought was that when you flick the preheat it supplies power to the circuit and when the genset starts up the alternator supplies power to the circuit and if that is the case then there could be an issue with the alternator where after a time it opens the circuit stops supply to this circuit and the genset shuts down. I have also had a chat with a guy yesterday that suggested that the fire suppression system is connected through the circuit and if so and there was an issue with that system it could be shutting it down.

 

Generally speaking....alternators, fire suppression systems and control boards are binary.....they either work or they don't. I believe your generator has a DC safety but again it doesn't fit the story you have told. Your voltmeter gauge would also show any problems with the alternator.

Sometimes a broken wire/connector can exhibit the issues you have but it eventually gets to the point that the generator won't run at all which makes it easier to find the problem. Broken wires are almost always DC + wires which have intermittent integrity. However, a broken wire does not fit your restart story. In most cases, a broken wire will restart fine and continue to run for a short while without the preheat switch.

It still is worthwhile to check the harness. If the generator will start and run, pull on the wire harness and connectors to see if it will shutdown.


Regarding the alternator:
R usually means: Exciter terminal where power comes from the purple wire to energize the alternator.
L usually means: Indicator Lamp

 

Hi to those who have tried to sort this issue out with me. Finally resolved today and is worth posting the issus incase anyone else has the same issue.
I went right through every cable to and from the gen set. Pulled out the start and pre heat switches and found the start/run switch had intermittent fault. Even pulled the carling switches apart and found contacts were quite burnt. So replaced the switches. Tried to start again and still the same. Ok here it is. My Sea Ray 500 is fitted with a Sea Fire fire fighting/suppression system. The system has a module in the circuit that automatically shuts the engines and genset down in the event of a fire. The module has a series of inbuilt switches that perform the task, one for each engine and one for the genset. As it turns out the switch for the genset was faulty. When you switch the genset to run the switch within the module engages and provides current to the run circuit through the switch to the genset. Unless there is a fire. The module being faulty was switching off after a few minutes. By passed the switch and all runs perfectly. Had it running for oner an hour fully loaded no problem. Have to order a new module which will fix the problem.

 

Glad you found your problem. Question, where is the module you are talking about located ? Also, when yours shut down, did the fuel solenoid close, like it was getting a signal to shut down. Ours doesn't, it acts like it is running out of fuel, the solenoid stays in the run position.

 

The module is located in the the dash cavity behind the steering wheel. It cuts all power to the run circuit on the generator meaning that the solenoid and lift pump don't get any power to run. Remember that our genset is controlled from the main panel in the salon. The power runs from the genset to the main panel and back to the genset (run Circuit) through the Sea Fire engine shut down system. The module also has running through it both engines, bilge blowers, and a number of accessories. A real pain when it goes out of wack. The you should have like I do, an override switch on a small panel, usually round somewhere near the dash. When you flick the switch to over ride it should bypass the module and allow you to start anything that is running through it. I tried that in the first place before I went digging only to find out it made no difference. I think it must just over ride for the main engines, not everything else. You can still start the fire system manually and I am thinking seriously of bypassing the module (auto fire all together) and just have the ability to manually turn it on if I ever need to.

 

One of the examples of how newer boats have become to complex. Keep it simple stupid is my motto. I'd by pass the module altogether.

 

Thanks for the info. I will chase it down. Maybe thats our issue also.