Black Smoke on Transom

[Brad Young]

Just got back from a 1 1/2 week trip in the sea of cortez. (My first cruise, Had a blast, the only complaint from my crew was, if you got an item to close to the Cold Blue Cold plate it froze. Nice problem to have.)

I wound up motoring about 20 hours. I notice a build up of black soot on the transmom (enough to write your name in) and the oil in the engine is about 1/8 below full. Normaling I do not motor more than 1 1/2 hour per month. So I have not notice any build up or low oil in the dipstick.

Question.
1)How much soot is acceptable?
2)Would you expect to lose 1/8 inch of oil in 20 hours of motoring?
3)If this is not normal what could be the cause?

P.S. I heard Black Dragon on the VHF but he could not hear me.

Thanks
brad

[Ron Hill]

Brad : Black smoke and soot on the transom means incomplete combustion.  
Try replacing the injectors, but if that doesn't help you might want to get a compression check.

[Ken Juul]

How many hours on the engine?  Is oil use normal?  A compression check will tell you the condition of the cylinders, leaky rings will cause oil burn.  Could also be oil coming down the valve stems on a high time engine.

Did you use a Cetane booster the last time you filled up?  Low quality fuel doesn't burn as clean.  Did you run at full power instead of 75%, full power tends to smoke more than cruise.

[waterdog]

Sorry I missed you!   Where were you in the sea?   We are on the baja side over in Santa Rosalia.    We have been routinely hearing VHF transmissions skipping over the Sea from San Carlos since Escondido...

[Brad Young]

Ken
1)I did not add a cetane booster. I will add next time I am on the boat.  What brand do you use?
2)Hours 2325. However I clocked 20 hours on my watch but the hour meter said 9.75 hours. So I may have more hours that I think.
3)I ran the engine between 1900 and 2200 rpm.

Waterdog: I sailed from San Carlos up to the Midriff Islands. San Fracisquito. Caleta Blanca, Isa Rasa then back to San Carlos.

All: A friend thinks I may be idling the engine to long. I usually let it idle until it reaches 180 or 190 degrees, before putting it in gear. How long do you all wait.

[Ken Juul]

Any cetane booster will work, stop by a truck stop and see what the big rigs are buying.  Truck stop or Wal Mart are going to be much less expensive than a marine store/fuel dock.

Diesels don't like to idle, that could be a big part of it.  I normally let the engine run for about 5 minutes while I get the nav gear turned on and working then let the lines go. 

[Stu Jackson]

I get everything ready, turn on the engine, go to the bow to release the bow dock lines, return to the cockpit (sometimes the tach hasn't started yet 'cuz of the 45 second delay from the regulator), release the stern dock lines, and go.  No idling at all.  I run at 2000 rpm for a few minutes while pulling up the fenders, then cruising speed at anywhere from 2250 to 2500 to 2600.  Sounds like you're really under loading your engine.

[Brad Young]

This is why I love this web site.
Thanks everyone.

On another note I got two stars by my name. Yoohoo!!!!  In another 20 years I may have as many as Stu.

[Mike and Joanne Stimmler]

One other thought is to make sure you have water coming out of your exhaust and to check the gauges to make sure things are normal. I also like to shift the transmission through forward and reverse while the dock lines are still attached.

[Ron Hill]

Brad : Idling the engine isn't good for a diesel and idling it below 1500rpm for any length of time is a killer.

[hump180]

Brad, changing our injectors helped us with this problem and also smoothed out the engine some.