Generator black smoke again, water intake issue?

[Bob Quinn]

This happened last year, my Onan 6.5kw started pouring out black smoke out of the cooling water exhaust. A fellow boater alerted us and yelled "Your on Fire!"

Thankfully it was not on fire.

It did it last year and never figured out why. A month or so later it started and has been running well since, until again last night.

Could this be the raw water intake is just plugged?

IF that is the case, wouldn't there be an overheating shut down sensor that should shut it down almost immediately? I don't know how long it was billowing black smoke, and it was only maybe 30 seconds before I ran down and shut it down.

I'm just wondering if it should have shut off immediately or would it have just kept running and cooked itself?

That or the raw water intake isn't the issue. I will find out just as soon as my old sore bones wake up enough to crawl down into the generator room.

Thoughts?

 

[Pascal]

Black smoke is not a cooling or water flow issue. Steam would indicate a raw water problem and yes if it gets too hot the gen will shut down. All gens have a coolant temp sensor which will trigger a shut down when coolant reaches a set temp. Many also have a raw water flow sensor which will shut it down as soon as raw flow is interrupted as well as an exhaust manifold temp senaor. It depends on the gen.

Black smoke is fuel. What load did you have when it happened? I ve seen it happen briefly under high load when additional loads come online like a big compressor starting

6.5 kw is very small, better make sure the heavier loads are off line

 

[dsharp]

Black smoke would usually be a sign of fuel not burning properly. The raw water output is easy enough to check. Are you getting an adequate flow of water from the exhaust? Is the exhaust riser warm to the touch? Is the intake strainer clean? I would be more inclined to have the injectors checked however that is usually not an intermittent problem.

 

[Bob Quinn]

Thanks guys, I will fire it up at the dock and see if it's still doing that.
I think we may have had 3 air conditioners running. Maybe that overloaded it or something.

I can check water flow visually once I fire it up.

Really didn't have time when this happened, it was more of an oh sh*t shut it down moment.

Thanks for the tips!

 

[Pascal]

Put a heavy load on it, incl water heater and stove. Also look for soot on the water

 

[Captain Ralph]

Thanks guys, I will fire it up at the dock and see if it's still doing that.
I think we may have had 3 air conditioners running. Maybe that overloaded it or something.

I can check water flow visually once I fire it up.

Really didn't have time when this happened, it was more of an oh sh*t shut it down moment.

Thanks for the tips!

Our lil gen-set can run fine all day, till the water heater (dual element) kicks on.
Pending the status of the ACs, the gen-set pukes black smoke or clamps down & stops running.
Open the water heater breaker, starts rite back up and continues to run fine.

 

[Pascal]

Our lil gen-set can run fine all day, till the water heater (dual element) kicks on.
Pending the status of the ACs, the gen-set pukes black smoke or clamps down & stops running.
Open the water heater breaker, starts rite back up and continues to run fine.

This is why I have never been a fan of under sizing generators. I want the additional capacity so it can put up with a sudden load. A water heater pulls a lot but has no surge when it starts like a big compressor.

My 18kw Norpro would be considered by some to be too big for a 53 footer but right now I have the WH and both 36k chillers running. When a chiller cycles off and on, the gen handles it with barely a miss. Each chiller runs at about 18 amp but spikes to 30+ when starting. I know… I m jinxing myself

 

[SEVEN]

Run it with everything but the AC on. Then add hot water heater then stove, then your dishwasher and washer/ Dryer. I think the 6.5 is too small for more than the 3 AC’s. Keep us in the loop.

 

[tom5518]

Could be a sticking injector. Are you sure it is only 6.5? Hatteras put 12-15 ones in at the factory.

 

[Bob Quinn]

Could be a sticking injector. Are you sure it is only 6.5? Hatteras put 12-15 ones in at the factory.

It might be a 7.5, we also have a larger one I think 17.5 possibly as the main generator, so I think this one was added as an extra.

 

[Captain Ralph]

It might be a 7.5, we also have a larger one I think 17.5 possibly as the main generator, so I think this one was added as an extra.

That makes sense, just a lil night gen-set.
We also run big/little gen-sets (plus inverter). Scheduled correctly, keeps the gen-sets loaded more correctly, hours down and saves fuel.