White exhaust smoke

[NIKBRUSH]

I have a 2007 Mainship Pilot 34 with a Yanmar 6lya-stp 370 HP engine, about 1430 hours. In neutral at 2000 rpm, after the engine is warmed up to 175 degrees F, it puts out a lot of white smoke, it not noticeable underway. In addition, at low rpm, there is a fuel exhaust sheen in the water at neutral. The fuel filters have about 30 hours and the vacuum gauge is ok. I guess, I have a fuel delivery system problem. From what I read, the fuel injectors should not need attention, but the valves probably should have been adjusted at 1000 hours. Would you start with the valves? Thanks.
Nick

 

[Comodave]

I am not an engine mechanic but if the 1,000 maintenance was not done I would start there and see if that helps. Besides they want the valves adjusted and the other work done for a reason.

 

[O C Diver]

Are you sure it's smoke and not steam? How is the exhaust water flow when it was generating the white stuff?

Ted

 

[NIKBRUSH]

Very strong water flow, all coolers HX, transmission, intercooler removed and cleaned, oil cooler replaced 6/22.

 

[SoWhat]

Hold a piece of stiff white paper or your hand at exhaust outlet if possible (or over the exhaust gas bubbles) If it feels slippery and has a fuel odor, then it is not steam but engine related and warrants investigation. Check oil levels and anti-freeze levels frequently.

A 'lot' of smoke would concern me. I get a slight sheen at startup and small amount of white smoke until warm up.

Engines are expensive, I would complete the 1000 hr maintenance cycle very soon starting with the valves. If that doesn't cure the problem a compression check would be in order. If I pulled the injectors I would probably send them out for testing.

 

[rgano]

Yanmar owner here. I would be doing both valve lash and injector inspection.

 

[Lepke]

Long term failure to adjust valves can lead to damage. Improper clearances also change valve timing. Valves with a gap too big open late and close early.

Injector tips can get buildups that interfere with the spray pattern. When the droplets are too big some of the fuel doesn't burn and ends up as a sheen.

Most injectors have a replaceable tip. Contaminated tips can be cleaned by soaking in a solution that dissolved fuel deposits. Using a quality fuel additive will stop tip buildups along with other advantages.

 

[MYTraveler]

In my experience, there are three colors of exhaust gas: black (resulting from incompletely burned diesel, most noticeable on mechanical engines under heavy acceleration, appears brown when the quantity of incompletely burned diesel is diminished), blue (but very light, easily mistaken for white unless you are looking for the blue (resulting from burned oil), and white -- steam (resulting from raw water meeting very hot exhaust gas). White steam can be distinguished from blue smoke based upon its dissipation -- steam dissipates quickly, blue smoke just gets diluted.

 

[rslifkin]

In my experience, there are three colors of exhaust gas: black (resulting from incompletely burned diesel, most noticeable on mechanical engines under heavy acceleration, appears brown when the quantity of incompletely burned diesel is diminished), blue (but very light, easily mistaken for white unless you are looking for the blue (resulting from burned oil), and white -- steam (resulting from raw water meeting very hot exhaust gas). White steam can be distinguished from blue smoke based upon its dissipation -- steam dissipates quickly, blue smoke just gets diluted.

White can be steam or actual smoke (steam dissipates faster). White smoke comes from totally unburned diesel, like a cylinder that's getting fuel but not firing.

 

[SteveK]

I had white smoke so I checked the raw water impeller which was coming apart. Replaced and no more white smoke.

 

[AdamC]

In my experience, there are three colors of exhaust gas: black (resulting from incompletely burned diesel, most noticeable on mechanical engines under heavy acceleration, appears brown when the quantity of incompletely burned diesel is diminished), blue (but very light, easily mistaken for white unless you are looking for the blue (resulting from burned oil), and white -- steam (resulting from raw water meeting very hot exhaust gas). White steam can be distinguished from blue smoke based upon its dissipation -- steam dissipates quickly, blue smoke just gets diluted.

So is a small amount of steam a problem? From my Yanmar 4LHA-STE's, I get a small amount of white steam from both. It dissapates/evaporates within a few feet of the exhaust exit. There's no persistent smoke and the engines sound great and jacket and exhaust temps are good.

-Adam

 

[MYTraveler]

So is a small amount of steam a problem? From my Yanmar 4LHA-STE's, I get a small amount of white steam from both. It dissapates/evaporates within a few feet of the exhaust exit. There's no persistent smoke and the engines sound great and jacket and exhaust temps are good.

-Adam

I think it indicates potentially excessive exhaust gas temps. Keep on eye on your pyrometers, and compare that to spec, if you can find a spec. In my case, I decided to take some pitch out of the props, even the the boat was already making full RPM. That dropped the temps a bit, reduced the steam and gave me some peace of mind.

 

[rslifkin]

So is a small amount of steam a problem? From my Yanmar 4LHA-STE's, I get a small amount of white steam from both. It dissapates/evaporates within a few feet of the exhaust exit. There's no persistent smoke and the engines sound great and jacket and exhaust temps are good.

-Adam

It depends somewhat on the engines and the exhaust elbow design. Some setups are just more prone to steaming than others. But as MYTraveler indicates, it could be caused by excessive exhaust temperatures.



If both engines steam about the same amount and it happens even when not under heavy load and the exhaust elbows have been confirmed to be clean and flowing adequate water, then I wouldn't worry about it.

 

[rgano]

I always have to calm myself down during the first cool weather run of the year when I get this big plume of steam out of my 6LPA-STP running at cruise.

 

[SteveK]

So is a small amount of steam a problem? From my Yanmar 4LHA-STE's, I get a small amount of white steam from both. It dissapates/evaporates within a few feet of the exhaust exit. There's no persistent smoke and the engines sound great and jacket and exhaust temps are good.

-Adam

Not usually, if you have an alarm on the exhaust hose to warn you of lack of raw water coolant flow.

One engine started the white smoke thing and then the alarm sounded. The raw water impeller was shot. New impeller and no more white smoke. It is a warning sign.