White Exhaust Smoke

[danielamartindm]

I have twin 29 HP Yanmar diesels my Leopard 39. One of them gives off what I deem a normal amount of white exhaust smoke along with the sea water. The other one gives off considerably more white smoke in the exhaust, especially at higher revs, along with a normal volume of exhaust water. The oil is normal in color, no whitish streaks or milky appearance, the coolant level is good, oil consumption is normal, and the engine runs smoothly and doesn't overheat. Both heat exchangers were replaced a year ago. What could the problem be?

[sailingunity]

I'm no diesel mechanic, mine gives off some white "smoke" but its really just water vapor as it dissipates quickly. I think its because my exhaust run is so short, the water doesn't have much time to cool down before exiting.

[danielamartindm]

Originally Posted by sailingunity

I'm no diesel mechanic, mine gives off some white "smoke" but its really just water vapor as it dissipates quickly. I think its because my exhaust run is so short, the water doesn't have much time to cool down before exiting.

It's quite a bit of smoke, though. If I didn't have another engine to compare it to, perhaps I wouldn't give it a second thought; but why is this engine producing so much more white smoke than the other one?

[BlackHeron]

White smoke simply indicates that all of the cylinders in your engine are in agreement as to who the next pope is going to be.

[four winds]

Maybe incomplete combustion since that can be white smoke. Maybe see if you can get a whiff of the smoke. To see what it smells like.

It might need the valves adjusted. If they have tightened up they may not be sealing good. Especially if it begins as the engine reaches temp. How many engine hours? If new, did it get the break in adjustment?

Also, maybe an injector is faulty. Constantly dribbling fuel, ...or poor spray pattern inhibiting combustion.

Or maybe a compression ring failed on one piston.

A three or four cylinder can still run smooth with one cylinder underperforming.

[StuM]

First things to do:
Grab an IR thermometer and compare the temperatures of the two engines (see first quote below)
Test the white smoke (see second quote below)

From:

https://www.cruisingworld.com/how/re...-smoke-signals

White smoke: This is one of the most difficult symptoms to diagnose because a number of factors can point to two general causes: overcooling, whereby the cylinder head and combustion chambers operate at a temperature that's too low for proper combustion; and piston-ring blowby, which indicates low compression and poor combustion.
White smoke represents atomized fuel, very small droplets of fuel that form a fog of sorts. It's common, and quite normal, to see this when a cold engine is started and until it warms up.
...
Other causes of white smoke are poorly adjusted valves or worn valve seats, a partially activated decompression lever, a blown head gasket, or a cracked cylinder head or cylinder liner. A mechanic with the proper tools can narrow down the suspects.

And here:

http://www.boats.com/how-to/diesel-e...lack-or-white/

White smoke can be caused by either excess fuel or an internal coolant leak in your engine. This is a case where you’ll probably want to call in the diesel pros, but here’s a diagnostic tip:

While the engine is smoking, hold your hand over the exhaust outlet for 20 seconds or so. Don’t restrict the exhaust, just attempt to coat your fingers with the smoke. Then hold your hand up close to your face. If you smell a strong diesel odor, the white smoke means the extra fuel is in such excess that it can’t even begin to ignite (as compared to black smoke, where partial ignition has occurred). Typically, this white smoke indicates a serious fuel injection problem.

If you don’t smell a strong diesel fuel odor, touch one of your fingers to the tip of your tongue. If you get a sweet taste in your mouth, stop right there: An internal coolant leak is indicated. (The sweetness is the antifreeze in the coolant, which is poisonous if you were to drink it.) This is also going to require the diesel doc unless you’re very handy yourself. What’s indicated is a blown head gasket or, in a worst-case scenario, a cracked cylinder head.

[nautitrix]

Is this the first time you've run your engine in cold weather? What are your thermostats doing. I'm sure you are not used to the weather we are having right now. Another option is that the fuel is sucking some air through some leaks in the fuel system. Ie. hoses, clamps, gaskets, and "O" rings. Check and see if the thermostats are up to snuff especially for this cold weather and then bleed the smoking engine and see if you have any air in the injector lines. What are the engine temperatures and is there a difference between the two engine temperatures. If there is a difference then you know where to look if there is no fuel issue. Are the levels of coolant dropping? Are they staying the same in both engines or is one dropping and one staying the same? If one is using coolant more than the other and it is the smoking one you may have a head gasket issue. You can of course call in the mechanics if neither of these are indicative of your problem. You are fortunate to have two identical engines to use for diagnostics.

[danielamartindm]

Originally Posted by StuM

First things to do:
Grab an IR thermometer and compare the temperatures of the two engines (see first quote below)
Test the white smoke (see second quote below)

From:

https://www.cruisingworld.com/how/re...-smoke-signals

White smoke: This is one of the most difficult symptoms to diagnose because a number of factors can point to two general causes: overcooling, whereby the cylinder head and combustion chambers operate at a temperature that's too low for proper combustion; and piston-ring blowby, which indicates low compression and poor combustion.
White smoke represents atomized fuel, very small droplets of fuel that form a fog of sorts. It's common, and quite normal, to see this when a cold engine is started and until it warms up.
...
Other causes of white smoke are poorly adjusted valves or worn valve seats, a partially activated decompression lever, a blown head gasket, or a cracked cylinder head or cylinder liner. A mechanic with the proper tools can narrow down the suspects.

And here:

Diesel Engine Smoke: Blue, Black, or White? - boats.com

White smoke can be caused by either excess fuel or an internal coolant leak in your engine. This is a case where you’ll probably want to call in the diesel pros, but here’s a diagnostic tip:

While the engine is smoking, hold your hand over the exhaust outlet for 20 seconds or so. Don’t restrict the exhaust, just attempt to coat your fingers with the smoke. Then hold your hand up close to your face. If you smell a strong diesel odor, the white smoke means the extra fuel is in such excess that it can’t even begin to ignite (as compared to black smoke, where partial ignition has occurred). Typically, this white smoke indicates a serious fuel injection problem.

If you don’t smell a strong diesel fuel odor, touch one of your fingers to the tip of your tongue. If you get a sweet taste in your mouth, stop right there: An internal coolant leak is indicated. (The sweetness is the antifreeze in the coolant, which is poisonous if you were to drink it.) This is also going to require the diesel doc unless you’re very handy yourself. What’s indicated is a blown head gasket or, in a worst-case scenario, a cracked cylinder head.

Thank you for taking the time to compose this very useful gem of information, Stu.

[danielamartindm]

Originally Posted by nautitrix

Is this the first time you've run your engine in cold weather? What are your thermostats doing. I'm sure you are not used to the weather we are having right now. Another option is that the fuel is sucking some air through some leaks in the fuel system. Ie. hoses, clamps, gaskets, and "O" rings. Check and see if the thermostats are up to snuff especially for this cold weather and then bleed the smoking engine and see if you have any air in the injector lines. What are the engine temperatures and is there a difference between the two engine temperatures. If there is a difference then you know where to look if there is no fuel issue. Are the levels of coolant dropping? Are they staying the same in both engines or is one dropping and one staying the same? If one is using coolant more than the other and it is the smoking one you may have a head gasket issue. You can of course call in the mechanics if neither of these are indicative of your problem. You are fortunate to have two identical engines to use for diagnostics.

Thank you for your reply, Nautrix. The coolant level on the smoky engine is right at the line and not dropping, but the white smoke does smell of diesel. I'm thinking it's either a compression problem, or a fuel injection problem, perhaps in just one cylinder. I will have a diesel mechanic look at it, I'm in over my head with this one.

[danielamartindm]

Originally Posted by BlackHeron

White smoke simply indicates that all of the cylinders in your engine are in agreement as to who the next pope is going to be.

Comic relief is always appreciated around boats.

[Wotname]

Originally Posted by danielamartindm

Thank you for your reply, Nautrix. The coolant level on the smoky engine is right at the line and not dropping, but the white smoke does smell of diesel. I'm thinking it's either a compression problem, or a fuel injection problem, perhaps in just one cylinder. I will have a diesel mechanic look at it, I'm in over my head with this one.

I don't know your level of mechanical ability but one check you probably could do is to measure the valve clearance and adjust if necessary.

Most likely this what the diesel mechanic would do as step one (after observing the symptoms).

[a64pilot]

Valve lash and or injection timing.
Yanmars are notoriously smoky, but it’s usually greyish blue, almost like oil smoke, but stinks of Diesel of course.
White smoke is usually water, however as has been stated if its water it dissipates very quickly, but fuel or oil of course doesn’t.