White smoke from diesel after one hour of operation

[workmaster2n]

I've got a cat with 2 Vetus M4.45 engines. I sucked a jellyfish into the starboard intake strainer last week, so I fished him out. Doing so, I realized the previous owner had made a frankenstein pipe from the sea cock to the strainer. The sea cock has a 3/4" barb on it, the strainer is 1/2" in and out. The water pump takes a 1/2" ID hose. So I found a 3/4" to 1/2" bushing and now have one 3/4" hose leading from the seacock the strainer, down through the bushing to 1/2", then 1/2" to the water pump.

We were on the boat this weekend, and for the first time in a while ran the engines for a long time. After 60 minutes, we noticed pretty heavy white smoke out of that engine. If I increased revs, we got more white smoke. The temperature gauge fluctuates between 70 and 80 degrees C on that motor, and sits at 80 degrees on the other motor. I think the gauge is a little sticky.

My understanding is that white smoke is usually caused by excess diesel in the exhaust, indicating the combustion chamber isn't hot enough. I'm a bit perplexed that this only happens after an hour of running the motor though (we confirmed this on the return trip, with the smoke only appearing after 60 minutes).

Another theory is that this could actually be steam. The exhaust exits the hull pretty much at the water line, so there's a decent amount of build up in the actual exhaust. Is it possible water is getting trapped from exiting freely and this somehow causes the exhaust to heat up or cool down, turning more water into steam?

Another theory is an injector is acting up, but why would that start only after an hour?

As far as I can tell, the engine runs healthy (starts easily, gets to the same top RPM it always has, doesn't burn excess fuel, temperature range seems normal), it's just this new addition of white smoke that is throwing me for a loop.

[Tin Tin]

Could be steam, clogged heat exchanger, clogged raw water through hull strainer or sail drive inlet, clogged elbow. We had this with barnacles in one engine intake, both running at 2800rpm (Yanmar 3YM30) one blowing steam, not the other, yet water ejection looked similar. Dove down cleaned out the inlet - no more steam.

[workmaster2n]

Originally Posted by Tin Tin

Could be steam, clogged heat exchanger, clogged raw water through hull strainer or sail drive inlet, clogged elbow. We had this with barnacles in one engine intake, both running at 2800rpm (Yanmar 3YM30) one blowing steam, not the other, yet water ejection looked similar. Dove down cleaned out the inlet - no more steam.

Any idea why it would take an hour to show up?

I’ll disassemble the water pump and heat exchanger next time I’m out to check for clogs, but just trying to wrap my head around this. Thanks for the info!

[Tin Tin]

No idea about why an hour. Guessing it might depend on ambient temperature, it could be taking that long for system to get hot enough. Have you got an infra heat heat reader/gun/thermometer to double check the gauge, and compare to other engine?

[deblen]

Does the white "smoke" rise rapidly from surface of water,leaving no sheen? It's steam.
or
does the white "smoke" stay down at water level,leaves a sheen,feels squeaky between finger & thumb & smells like fuel?
It's raw unburned fuel.
Is there the same amount of water coming out exhaust of both engines at same RPM?

Cheers/Len

[Tupaia]

White smoke typically leads you to injector issues however 1 hour period is odd.


How much fuel do you have in the tank could it be that the fuel is getting hot after a period due to the return line and the increase in temperature is affecting the injector.


But just guessing really.

[HeywoodJ]

Originally Posted by deblen

Does the white "smoke" rise rapidly from surface of water,leaving no sheen? It's steam.
or
does the white "smoke" stay down at water level,leaves a sheen,feels squeaky between finger & thumb & smells like fuel?
It's raw unburned fuel.
Is there the same amount of water coming out exhaust of both engines at same RPM?

Cheers/Len

This. Knowing whether it is smoke or steam is critical to diagnosis. One other thing, in calm conditions steam tends to dissipate relatively quickly (except in very humid climates), smoke tends to stick around 'longer' (which is subjective and hard to evaluate if you have never dealt with either before).

As for why an hour? There is almost enough raw water flow for cooling. Just barely under the required amount. You say you sucked up a jelly fish, and changed out plumbing. Are you sure you cleaned out all obstructing pieces of debris? With the plumbing changes, are you certain you don't have any air leaks? The suction side of the pump works under vacuum, so quite possible to have air leaking in without water dripping out, especially if any components are above the waterline, reducing water flow.

[CruiserUser]

I had white steam on one of my Volvo D2-40s lately, starting after quite a while, like described here.
My water filters have a clear cover, and are normally filled all the way. On that motor, the filll level was lowering significantly during operation, but once the engine was stopped it "jumped" back to full. I am pretty sure that was vacuum built up by the sea water pump, trying to get enough water. That is something you could check, it would be a sign that the water inlet is the problem.
I had the boat out of the water, closed the water inlets of the saildrive, and treated the saildrive with decalcifier for professional dish washers, not agressive to metal. Quite heavy bubbles coming up the tubing for a while, so a lot was obviously in there to dissolve. Afterwards problem was gone.
I guess that process might work while in the water also, filling the decalcifier through the sea water filter backwards into the sail drive, but never tried that.

Maybe worth a try. If it is not the problem, it will also not do any bad. Good luck.

[skipperpete]

“Sucked up a jellyfish” suggests that the raw water pump ran dry so perhaps taking off the cover plate for an impeller inspection would be worthwhile. Did the incident cause an engine overheat? How did you know that the seawater intake was blocked?
Unless Vetus uses “Globe” impellers I suspect missing blades.

[workmaster2n]

Originally Posted by Tin Tin

Have you got an infra heat heat reader/gun/thermometer to double check the gauge, and compare to other engine?

Good call. I'll double check with the infra heat gun next time to confirm the gauge is working.

[workmaster2n]

Originally Posted by Tupaia

How much fuel do you have in the tank could it be that the fuel is getting hot after a period due to the return line and the increase in temperature is affecting the injector.

We've got about 40 liters left in the 80 liter tanks. It was getting warm, but not oppressively warm. But it's something I'll keep an eye on!

[workmaster2n]

Originally Posted by deblen

Does the white "smoke" rise rapidly from surface of water,leaving no sheen? It's steam.
or
does the white "smoke" stay down at water level,leaves a sheen,feels squeaky between finger & thumb & smells like fuel?
It's raw unburned fuel.
Is there the same amount of water coming out exhaust of both engines at same RPM?

Cheers/Len

I'd say the "smoke" stayed near the surface, but it did disappear pretty quickly. Hard to tell if there was a sheen, the waters where the boat is are pretty foul.

I didn't think to test the smoke to see if it's squeaky between the fingers. That's a great test. Will do that next time.

I'd say about the same amount of water came out of both engines. And fuel burn rate seemed to be about the same (we don't have any sort of fuel flow gauge though).

[workmaster2n]

Originally Posted by CruiserUser

I had white steam on one of my Volvo D2-40s lately, starting after quite a while, like described here.
My water filters have a clear cover, and are normally filled all the way. On that motor, the filll level was lowering significantly during operation, but once the engine was stopped it "jumped" back to full. I am pretty sure that was vacuum built up by the sea water pump, trying to get enough water. That is something you could check, it would be a sign that the water inlet is the problem.
I had the boat out of the water, closed the water inlets of the saildrive, and treated the saildrive with decalcifier for professional dish washers, not agressive to metal. Quite heavy bubbles coming up the tubing for a while, so a lot was obviously in there to dissolve. Afterwards problem was gone.
I guess that process might work while in the water also, filling the decalcifier through the sea water filter backwards into the sail drive, but never tried that.

Maybe worth a try. If it is not the problem, it will also not do any bad. Good luck.

I checked the strainer when the engine was running. There are little "bubbles" near the top, but those appeared to be about the same on both motors.

We have shaft drive, so nothing to check there in terms of fouling. Plenty of water seems to flow when I disconnect the strainer and open the sea cock, but it's worth a check to see how clean the inlet is looking.

The heat exchanger is a year old, but sending some descale through it probably isn't the worst idea in the world.

[workmaster2n]

Originally Posted by skipperpete

“Sucked up a jellyfish” suggests that the raw water pump ran dry so perhaps taking off the cover plate for an impeller inspection would be worthwhile. Did the incident cause an engine overheat? How did you know that the seawater intake was blocked?
Unless Vetus uses “Globe” impellers I suspect missing blades.

We got lucky and the jellyfish got sucked up about a minute after we started the motor. We checked the exhaust and saw water was coming out, then were sitting up front tidying some lines when we heard a change in exhaust sound. Looked overboard and saw nothing appeared to be coming out. Gave the motor a few more revs to see if there was just low pressure, then stopped the motor. I don't think the gauge even read 60 degrees when we turned the motor off. We got lucky there.

When I took the lid off the strainer, I noticed water wasn't pooling out like it has done in the past when I've cleaned the strainer. We closed the seacock at that point. When I took the strainer out, I found part of the jelly fish. Cleaned the strainer, opened the sea cock, and no water came out (even though we were below the water line). Once I took the strainer off, we opened the sea cock again (with just the hose attached). Again, not water. So we took the frankestein hose off and looked down and saw the rest of the jellyfish (RIP). Shook him out, reattached everything, and voila, water!

Good call on the impeller. Even though it only ran for a few seconds, may have been enough to kill it. Good call on that!

[workmaster2n]

Thanks for all the ideas!