Black Smoke?

[pateco]

Yesterday on our way out to our weekend races, My 1983 Yanmar 2GM dropped down from 3000 RPMs to 2000 without me adjusting the throttle, and began to produce lots of black smoke. We were almost out to the race course, so I hoisted sail, killed the engine and determined to investigate more when the races were over. Once races were completed (we got our second first place), I restarted the engine, and had good throttle control, and no smoke. Since it was again running correctly I headed back in and towards our dock. About an hour later as we neared our canal entrance off of the ICW the motor again dropped to 2200 RPM and started smoking. I lowered the throttle hoping to make it back to the dock, but it eventually stalled completely and wouldn't restart. I dropped anchor in the ICW and began to try to figure out what was wrong before I called TowBoat US. I have no fuel gauge, so one of the first things I checked was fuel level. We were out of diesel. I refilled with fresh diesel form the Jerry can I keep aboard, I re-primed, and she started right up and acted normal again all the way to our dock.

My question is, can a low fuel event cause black smoke? Could it be the dregs in the bottom of the tank causing some sort of clog that causes black smoke? The loss of power due to low fuel I can understand. It is the black smoke that has me puzzled.

I plan to replace both of the fuel filters before we go out again, and will let you know if they were dirty. They are only about a year old. There was no visible water in the Racor, but there was a very small amount of sediment in the bottom.

This is a raw water cooled 2GM 13hp. I had the short mixing elbow off two weeks ago while I installed a brand new fuel lift pump, and there was no appreciable carbon build up.

Any insights into this issue would be greatly appreciated.

 

[jssailem]

Chip
In the past 2 years I’ve stalled my 4 cyl Perkins out a few times from fuel starvation. Most of the time for me there has been a slight surge in the engine rpm the a stutter. What you describe is normal. Black smoke usually comes from oil. Starving the engine may be sucking in oil around the rings and trying to burn it. The dirt in my tanks would clog the filters. This also contributed to fuel starvation. I now have a vacuum gage installed on the fuel line. It lets me know when the filter is getting clogged.

Check your fuel filter. Fill your tank. And go forth counting your fuel consumption like @Stu Jackson does. He keeps a detailed log and nearly never runs out of fuel. Did hear he was pretty low once though.

 

[Rich Stidger]

Speculation: Could a fuel starvation cause the engine governor to advance for more speed but the load wouldn't let it. That would be very similar to an engine overload condition which does cause black smoke. What do you think?

 

[Kermit]

Black smoke means no new Pope, yet.

 

[Benny17441]

Cause or effect? The same way a load increase can cause overfueling a sudden loss of RPM at constant throttle seems could result in the same.

 

[Stu Jackson]

Did hear he was pretty low once though.

True, but that was after a 13 hour day from Ilwaco to Greys Harbor and another one from Greys to Lapush. 23 gallon tank, I figure 20 useful, 0.5 gph, 40 hours (with that reserve of 3 gallons), 5 knots 40 hours, do the math for range.

 

[jssailem]

So @Stu Jackson so it was more than once that it happened...

Who would have thought?

@Kermit... Black Smoke??? A pope? Sound like a comedian going for the laugh...

 

[dlochner]

True, but that was after a 13 hour day from Ilwaco to Greys Harbor and another one from Greys to Lapush. 23 gallon tank, I figure 20 useful, 0.5 gph, 40 hours (with that reserve of 3 gallons), 5 knots 40 hours, do the math for range.

So @Stu Jackson so it was more than once that it happened...

Who would have thought?

@Kermit... Black Smoke??? A pope? Sound like a comedian going for the laugh...

http://www.wemausa.com

 

[Stu Jackson]

So @Stu Jackson so it was more than once that it happened...

We refuled at Greys Harbor.
Poin tbeing, if we hadn't, two 13 hour days is 26 hours and I have 40 hours of fuel in the tank plus the reserve.

That's all.

Time for a shower and crash. In Bedwell now.

 

[jssailem]

Thanks for the link.
That is a sensor in my future... Well 2 sensors actually. I have two tanks.. listed as 89 gallons each.

Man I could be come a fuel dock if we cruised together and still make it home.

 

[dlochner]

Thanks for the link.
That is a sensor in my future... Well 2 sensors actually. I have two tanks.. listed as 89 gallons each.

Man I could be come a fuel dock if we cruised together and still make it home.

You can carry 178 gallons of diesel? I thought I had a lot at 40 gallons.

The Wema sender is a nice unit, reliable and accurate. It is not subject to the problems that the typical Moeller float sender has. I've had 2 of them fail when they get soaked with fuel.

 

[jssailem]

Yes Dave... Sounds crazy on a Sail boat.. At least that is what I thought when I bought the boat.

Then I started to cruise the waters up here and learned in the Summer the winds can be fickle but the tidal currents are there like clockwork. You can be sitting in a zephyr waiting for the wind to spring up and suddenly your moving at 5 knots in the current and increasing down towards the rocks, whirlpools, and tidal falls as the Ocean pulls/pushes the water in and out of the Salish Sea.

If it ever comes to be, I figure I can motor nearly half way to Hawaii. At least enough not to sit in the doldrums and get into the trade winds..

 

[dlochner]

If it ever comes to be, I figure I can motor nearly half way to Hawaii. At least enough not to sit in the doldrums and get into the trade winds..

People will think you're daft if you leave for Hawaii without a dozen yellow diesel containers lashed to the lifelines, little will they know.

 

[jssailem]

Who knows the maybe correct...

 

[Davidasailor26]

I think black smoke is usually unburnt fuel. Oil would be blue smoke. If the engine were starving for fuel it wouldn't have unburnt fuel in the exhaust, just loss of power. Also fuel starvation wouldn't explain the fact that it ran fine for a while after the race. My bet given that in both cases it happened after a long run is on overheating. An overheating engine will leave unburnt fuel and less power just like you saw. Do you have a temperature gauge, or did you notice if your exhaust water flow was adequate?

 

[All U Get]

Black smoke means no new Pope, yet.

I thought it meant I was selected pope.

 

[JohnShannon]

I think the way it works is your "throttle" lever is really just an RPM setpoint. So In your case you set for 3000 and the governor system injected enough fuel to make that happen. Then the RPM fell out of regulation and the governor goes "balls to the wall" and adds as much fuel as it can to bring the RPM up to stepping. Lots of unburnt fuel = black smoke and no pope. I guess in your case you had intermittent fuel delivery ie. none (so RPMs drop) followed by as much as the system could deliver (= black smoke / overfilled)

 

[kaptainkenny]

Yesterday on our way out to our weekend races, My 1983 Yanmar 2GM dropped down from 3000 RPMs to 2000 without me adjusting the throttle, and began to produce lots of black smoke. We were almost out to the race course, so I hoisted sail, killed the engine and determined to investigate more when the races were over. Once races were completed (we got our second first place), I restarted the engine, and had good throttle control, and no smoke. Since it was again running correctly I headed back in and towards our dock. About an hour later as we neared our canal entrance off of the ICW the motor again dropped to 2200 RPM and started smoking. I lowered the throttle hoping to make it back to the dock, but it eventually stalled completely and wouldn't restart. I dropped anchor in the ICW and began to try to figure out what was wrong before I called TowBoat US. I have no fuel gauge, so one of the first things I checked was fuel level. We were out of diesel. I refilled with fresh diesel form the Jerry can I keep aboard, I re-primed, and she started right up and acted normal again all the way to our dock.

My question is, can a low fuel event cause black smoke? Could it be the dregs in the bottom of the tank causing some sort of clog that causes black smoke? The loss of power due to low fuel I can understand. It is the black smoke that has me puzzled.

I plan to replace both of the fuel filters before we go out again, and will let you know if they were dirty. They are only about a year old. There was no visible water in the Racor, but there was a very small amount of sediment in the bottom.

This is a raw water cooled 2GM 13hp. I had the short mixing elbow off two weeks ago while I installed a brand new fuel lift pump, and there was no appreciable carbon build up.

Any insights into this issue would be greatly appreciated.

Had the same experience a couple of years ago with my H31. Attributed the black smoke to poorly combusted oil deposits at the bottom of the tank. You just figured it out quicker than me.

 

[MitchM]

the worst black smoke i ever saw was when the single cylinder fary mann engine burned its single exhaust valve. that was the end of that engine....

 

[Capt Robbie]

Bad fuel or sludge/ algee from bottom of tank will cause black smoke. Because it flashes off at a faster rate then newer fresh fuel, algee may have gotten past fuel filters. The filters are mostly going to stop grit and dirt. Algee sludge is a much finer partical then dirt.
Black smoke I unburned deisel fule. Oil is usually grey or blueish in color.