Diesel Smoke Question

[KayW]

We have a Westerbeak 28HP engine in our 1983 Gulfstar sailboat. We are finding that when we hit the throttle to full speed it puts out a significant amount of black smoke.... but when we bring it back down to cruising speed it goes away.... any thoughts about this?

Thanks

[Ex-Calif]

Black smoke generally indicates unburned fuel. For an engine that has been operating normally it is often an indication that the bottom or prop is fouled. The other symptoms that go with this are inabililty to make full rpm or low boat speed.

If rpm and speed are ok it could then indicate a fuel delivery problem - dirty/leaking injectors being the prime target.

How is the rpm and boat speed? When was the last time someone dove on the hull and had a look?

[KayW]

Thanks for the swift reply.

We just had the bottom cleaned (after we noticed the smoke) on our quarterly maint. plan. They did note that they found (and cleaned) light growth on the propellor and shaft, but the propeller passed rotation test and Cutlass Bearing was checked and had no play. As I mentioned, this was after we noticed the smoke, and we have not run it since to see if the smoke is still there.... could that light growth have caused enough fouling to cause any black smoke?

[cantxsailor]

With even a light coat of critters on my prop my Ynamar would smoke. Run it and call us back.........m

[Sailmonkey]

An older engine with less than perfect compression will also smoke at full load. If this is something new, ie just appeared after using the boat, this may be a problem. However if this in an '83 engine with a few hours on it I wouldn't get too excited. Also an engine may smoke excissivly for a while if it has many hours of light loading, this will be more of a grey haze rather than dark black.

[KayW]

Since we have only owned the boat for about 10 run-hours we do not know its history. We really just noticed the smoke "staining" the stern of the boat and then a friend in another boat behind us mentioned it... And now that we know, we have noticed it ourselves.... under full throttle. It starts instantly, sounds/runs so smoothly, and just purrs..... We will run it next weekend and see if the "cleaning" made a difference. Hopefully that it is.... One final thing, if there is a major "Problem" I would think that we would first experience some diffuculty in starting, noise or rough running/idle, right?

[Tellie]

Check your exhaust elbow as well.

[MarkJ]

Originally Posted by KayW

Since we have only owned the boat for about 10 run-hours we do not know its history.

Hi Kay

Soon after we got our boat we had a factory trained mechanic give our engine a 1 hour ‘once-over’ and were very pleased Its money well spent. After that all our maintenance has been trouble free and we feel confident with the engine.

Just remember one thing: sometimes the less scrupulous mechanics will say that your whole engine is shot and you need a new one for $15,000 etc. Just don't believe them It does mean you have wasted your money on an idiot.

Perhaps ring the Westerbeke specialist and ask the price for a 1 hour service.

Mark

[Chief Engineer]

Ever notice how a dump truck smokes...pulling away from alight?

Big load, lotsa fuel, not all of it burning.

Calculate your theoretical hull speed.

If you try to push past that, you will have black smoke.

[meyermm]

I second Chief engineer. From your description you do not say whether the smoke continues or is only prevalant for a few seconds after you open the throttle?

[KayW]

As far as we were told by the fellow behind us..... it only lasted for just a bit (don't know seconds....) and then it went away. And it does not happen at all at cruising speed....

[meyermm]

Sounds like typical diesel! Firstly open the throttle slowly regardless of engine condition. Secondly I would get the engine serviced by a competent Diesel mechanic. Make sure all the filters are changed, tappets adjusted and have the injectors serviced with new nozzles. A compression test would also be appropriate. Have the engine oil and filter changed. Even if the engine appeared to be operating ok you would be wise to have this done as a starting point for you.

[Stillraining]

Black smoke is a lack of sufficient air for the amount of fuel you apply to the cylinders or simply stated as "over fueling".... And it is caused by several different ways... one of which is indeed as In Chief engineers dump truck example..another is a clogged air filter.yet another as EX-Calif says bad injectors...in Chiefs example it is because the driver is starting off in too high of a gear for the weight on-board there for lugging the engine with his foot mashed to the floor...take a peak in that cab and you will most likely find a young buck with his hat on backwards and all the air let out of his suspension seat so he is riding low and looking cool.....Shifting all day long is tiring..and if the truck will pull from a stop in 3rd they will use it and not 1st gear as they should...that cuts off about a thousand shifts during the day.

You are basically doing the same thing by advancing your throttle to quickly as the propeller grabs big bites of water with little compensating forward motion through it...or in other words your lugging your engine too.,until the boat comes up to speed allowing the prop to increase speed which allows the engine to increase speed which finally in turn allows it to BREATH or suck in enough air for the amount of fuel your asking it to try and burn.

FWIW ,truly unburnt diesel fuel is white out the exhaust..a good sign of a bent rod as a mater of fact...why? no compression no fire.

We have little risk of this... but that truck driver can actually over fuel his engine enough to actually burn holes in his pistons..I have had to retrain every truck driver I have ever hired...most have a mentality of " It ain't my truck"...I made it their truck from day one.

[Boracay]

I'd also suggest changing the transmission oil (and filter if applicable).

If you're seriously worried maybe consider checking that you can get full revs with the pitch on your prop.

[ragdoll]

Sounds like the engine is running like an older diesel engine to me. The newer models are cleaner. Enjoy it. Love that diesel smoke. yuk!