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Old 07-04-2017, 10:06 AM   #1
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V-504 bit of blue smoke under heavy load

Is it normal for older Cummins V-504-M engine to have a bit of blue smoke under the heaviest load (transition to planning), before that and after that, no smoke at all. I was expecting more of a black smoke in such conditions, but it seems to me that it is more blue (oil) than black.

Boat is heavy semi-displacement (around 4000 kg), engine is set at 195HP/3000RPM. If there are two people on board, it is just a puff of smoke in the transition, but with maximum of 8 people on board there was smoke for a longer period, while the boat did not pass the hump. After the hump, engine is rotating easy, passing the maximum RPM, like it could have a higher pitch prop, but it would probably be overloaded in transition to planing and could break the gears inside outdrive, so I would not dare changing it, except to lower maybe.

Engine is not using oil at displacement speeds, neither at planing with two people, but it did use some oil after the ride at planning with 8 people on board (again, not alarming, but it did). Anyway, my preferred and mostly used speed is displacement speed, but I was curious about specifications and performance of boat and engine and to check that everything is OK.

Could this be:

1) due to overload (although black would be expected);

2) "improper" oil (Mineral oil "Total Quartz 5000 Diesel 15W40"), changed at 50 hours, 100 hours, next change planned at 200 hours and after that I do plan to change once per season because of the way I use the boat (oil and fuel filter changed at same intervals); I am winterizing the boat each season;

3) some mechanical problem like worn valve seats/guides, incorrect injector setting (engine was overhauled in 2014. and boat launched in 2016. and since than I made about 170 hours, therefore doubt cylinder glazing or bad compression in question);

4) lack of air in engine room, I will try to open the hatches during the transition process, but I presume that this should also give black smoke, or am I wrong? (there are enough air openings when area calculated, but not so sure about ideal positions in the engine room, so I am guessing as one possibility, then again, after the hump, engine is rotating easily and no smoke)

5) something else, what?

The most important for me is to check if this means that I should correct something to prevent future problems or do nothing if this is normal with older type mechanical engine. Again, have in mind that I will 99% of time drive at displacement speed, but I presume that it can mean that some setting is not correct which can only be seen at heavy loads which could reflect on engine in the long term.

I would appreciate your opinions on this.
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Old 07-05-2017, 05:43 AM   #2
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"due to overload (although black would be expected);"

Just watch almost every sport fish as they power up in the plane.

Almost all will blow dark smoke from an "overload" for the time till they get on top of the water.

No big deal, if its just to get on top, but it is a big deal if constant at cruise.

"Engine is not using oil at displacement speeds, neither at planing with two people, but it did use some oil after the ride at planning with 8 people on board (again, not alarming, but it did)."

Every engine in the world uses oil bar none.Every power stroke oil left on the cylinder walls gets burned.

The usual reason folks do not think their engine uses oil is blowby will condense in the oil pan so the oil quantity looks OK on the dipstick reading.

That's why engine mfg require oil changes after certain intervals.

Sounds normal to have oil "consumption" higher at heavy loads , as there is frequently less blowby at higher loads from the rings sealing better , and higher oil temperature that may remove some of the condensate.
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Old 07-06-2017, 03:46 AM   #3
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Quote:
Originally Posted by FF View Post
Every engine in the world uses oil bar none.Every power stroke oil left on the cylinder walls gets burned.

The usual reason folks do not think their engine uses oil is blowby will condense in the oil pan so the oil quantity looks OK on the dipstick reading.

Sounds normal to have oil "consumption" higher at heavy loads , as there is frequently less blowby at higher loads from the rings sealing better , and higher oil temperature that may remove some of the condensate.
Thanks FF!!
Haven't thought of it that way. Than I would not touch anything except following servicing routines and oils/filters change intervals according to mfg specs. And yes, there is smoke only during transition at the worst hull angle, otherwise no smoke at all.
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