Minor smoke in exhaust of 1998 450DA Cat 3126's

I've noticed a minor plume of smoke when running up in the 2,000 RPMs range and believe it's from the port-side engine. Any thoughts on a root cause? Bad injector? Bad fuel? Just began noticing this last week. I'm going to add some additive to hopefully clean out the injectors.

What color was the smoke?
Was the boat under load or just run up at the dock when you noticed the smoke?
Is there any sooting on the transom?

Seemed to be a whitish-grey. It only occurs when I'm up on pad running 2,000+ RPMs. Haven't noticed too much soot build-up.

fwebster said:

What color was the smoke?
Was the boat under load or just run up at the dock when you noticed the smoke?
Is there any sooting on the transom?

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The last 2 runs I made I noticed the same grey/white smoke, along with the sooting on the transom (and dinghy mounted there). Port engine seems to be a bit smokier though they both do, and the soot build up seems more on port as well. Anything I should be concerned about with it you think?

Grey-white smoke is usually steam in the exhaust . That is caused by the hot exhaust cooling water mixing with cool seawater. Are your impellers fresh? What about the engine temps? Does the engine temp rise to 195˚ and stay there or does it continue past there until you pull back the throttle. Cat engines have a lot of cooling capacity but when the cooling sustem needs attention, they will run up past 195. Another less likely cause is a blown head gasket. A blown head gasket brings on other symptoms like disappearing antifreeze and a sweet odor to the exhaust.

Sooting on the transom comes from overloading the engine or from restricted intake air....check the breather element and replace or wash it depending on the type. A fouled aftercooler will also cause sooting.


Disclaimer: Y'all realize that I am 2500+ miles away from either of you and have not been on either boat, so the above is a generic educated guess based on what usually happens with 3100 series Cat engines.

DJ,

How many hours on the engines? I had ~800 on my 3126 before encountering the dreaded "Belgian" (or "French") block issue....

Christopher,

1,500 hrs

IMO the true marine diesel source of information is BOATDIESEL.COM Tony Atkins of Seaboard Marine (sbmar.com) is one of the moderators. All others on this site are mostly owners offering only opinions. Check it out if you think you have a real problem.

Clemson said:

IMO the true marine diesel source of information is BOATDIESEL.COM Tony Atkins of Seaboard Marine (sbmar.com) is one of the moderators. All others on this site are mostly owners offering only opinions. Check it out if you think you have a real problem.

Click to expand...

Yeah, Frank is just guessing. Of course he is just giving opinions. Anyone who attempts to diagnose an engine issue on a forum is giving their best guess. Until a certified mechanic verifies the problem, everything is just an opinion, offered by some pretty knowledgeable people that I would put against anyone on the other site you referenced. That is a site with a wealth of information but they can only give opinions as well without seeing the boat. BTW, I trust what Frank Webster has to say more than 98% of any opinions from forums, magazines or even certified mechanics. Trust me on this one...

It appears that 40 years of owning, running, maintaining and repairing Caterpillar, Cummins, Kubotas, Yanmar, Ford, International, Lombardini, Perkins, doesn't count. I'm just wasting my time here since I have been discounted as just guessing when I answer peoples questions. Y'all work this out on your own. Ive got getter things to do...........

I was watching Clemson yesterday evening as he added 25% more posts to his count. I’m wondering if he was in his cups a bit.:lol:

I doubt he has spent enough time here to learn who knows their stuff, but the reality is that his post recommending boat diesel is a good one. It’s another great place to go for ‘opinions‘.

I don’t think anything should be taken personal. His suggestion might have been triggered by this just a couple posts before his. I get what it means…maybe he didn’t.

fwebster said:

Disclaimer: Y'all realize that I am 2500+ miles away from either of you and have not been on either boat, so the above is a generic educated guess based on what usually happens with 3100 series Cat engines.

Click to expand...

fwebster said:

Grey-white smoke is usually steam in the exhaust . That is caused by the hot exhaust cooling water mixing with cool seawater. Are your impellers fresh? What about the engine temps? Does the engine temp rise to 195˚ and stay there or does it continue past there until you pull back the throttle. Cat engines have a lot of cooling capacity but when the cooling sustem needs attention, they will run up past 195. Another less likely cause is a blown head gasket. A blown head gasket brings on other symptoms like disappearing antifreeze and a sweet odor to the exhaust.

Sooting on the transom comes from overloading the engine or from restricted intake air....check the breather element and replace or wash it depending on the type. A fouled aftercooler will also cause sooting.


Disclaimer: Y'all realize that I am 2500+ miles away from either of you and have not been on either boat, so the above is a generic educated guess based on what usually happens with 3100 series Cat engines.

Click to expand...

Understood Frank, I appreciate your advice, it gives me starters on things to look at.

I noticed that you only have a few posts on CSR yet you have been around since 2010. You may not be aware of the oil issue with 3116/3126 Caterpillars, and it can indirectly cause sooting on the transom.

When the 3116/3126 was first released in the mid 90's Caterpillar recommended the uses of a multiviscosity engine oil like a 15W40. Sometimes later, toward the end of the 90's, Cat changed the fluid recommendations specify that 3116/3126 owners use only Cat SAEO oil (Special Application Engine Oil - a synthetic packaged for and sold by Caterpillar dealers in single viscosity SAE 30 or SAE 40 depending upon your ambient temperatures) or a commercially available oil like Shell Rotella T or Chevron Delo 400 in either SAE 30 or SAE 40. Caterpillar discovered that on marine engines that are aftercooled and turbocharges, the viscosity index inhancers contained in the multiviscosity oil to allow it to change viscosity as the oil gets warm tend to break down and become deposited on the internal passages of the aftercooler and turbo vanes thus restricting intake air flow and causing sooting on the transom.

You can read what Cat says in their Fluid Recommendations here: Cat publication # SEBU 6251-8, March 2004. Caterpillar, unlike a lot of other engine makers, keeps their fluid recommendations current as technology and market conditions change. The above referenced publication is now up to version 17, dated September 2014, but most of the 3116/3126 explanation is omitted with a footnote asking readers to check with their local dealer. The current recommendations are the same as in the SEBU6251-8. 2004. This is kind of a "check this box last" in solving a sooting issue.

The usual cause if just simple overloading. We tend to take stuff to the boat every time we go but never bring it all home. Our boats get heavier with the load we put on them and that coupled with Sea Ray's tendency to over prop boats usually mean we need to keep a constant eye on WOT rpms and have our props re-pitched when we can no longer achieve rated rpm's of 2800. THe test is simple and won't hurt the engines......with your normal load of people, fuel, water, gear, etc. on the boat, find some open water that is reasonably smooth and open the throttles to the stops and record the maximum rpm's each engine achieves, then pull the throttles back to 2400 rpm and check the engine temps to see how much the engines cool down. Sea Ray tweaked the props in the mid-late 90's with 2 adults, 50 gal of fuel, no water, no waste and only a Coast Guard gear bag full of life jackets and safety gear. It isn't unusual to find boats that top out at 2600-2700 rpm which indicated the engines are overloaded and that will certainly cause sooting.

In your case, I suspect he white grey smoke is nothing more than steam, but it could be caused by inadequate cooling water flow. Checking the engine temps at WOT and seeing if they cool down a lot when you slow down may give you an indication that your impellers need attention. We run out boat 120-150 hours per year and I'm getting about 200 hours out of my impellers, so we change them every other year.

Hope the above helps and good luck running down the smoke/sooting issues...............

Thank you for all your amazing answers/ideas Frank! You truly are invaluable to this site!

On another note, we were heading back yesterday, cruising at about 2,200 RPMs, an noticed it to be more of a black smoke. Also noticed some sooting on the portside transom. Anything different?

Black smoke with a diesel usually means unburned fuel in the cylinder. The source could be turbo related or could be as simple as carbon on the tip of an injector that is disrupting ability of the injector to atomize the fuel. If the fuel leave the injector in droplets instead of a fine atomized spray, you will get black smoke.

This isn't a problem to put up with or to procrastinate in getting a diesel mechanic on the boat to properly diagnose what is going on. When fuel enters the cylinder but doesn't get completely burned in the combustion process, the remaining fuel will wash the lube oil off the cylinder walls and you get very accelerated cylinder wear. You will see fuel in the lube oil and very likely high iron and chromium in your oil sample. So, it would be a good idea to call your Cat mechanic pretty soon on this one.

Great, very helpful post, thank you so much Frank. To answer your question about my membership, I had a SeaRay previously, left for a few years while owning a Regal, and just this year bought another SR, which is my current boat. I tried to do as much of the research I could online prior to purchasing my current 370EC, including a bunch here on CSR, mostly targeting the Cat 3116s. I also hired a surveyor and did an extensive sea trial. One thing the surveyor did was to crawl down below during the sea trial and take temps on the important bits on both engines. We were fairly lightly loaded (I think the water was empty, the boat was cleared of excess) but there were 4 of us aboard and we had about 7/8 tanks of fuel. Given that, we are much heavier now (I always keep the water tank full, there's almost always something in the holding tank when cruising, dinghy hanging off the swim platform, all of our amenities, etc), so it wouldn't surprise me to see that it's a load thing.

I haven't done the WOT test yet, but will, that should tell me if we're overloaded.

The numbers the surveyor got during trial are:

SEA TRIAL ENGINE INSTRUMENT READINGS
RPM:
Port= IDLE: 600 SLOW: 1500 CRUISE: 2300 WOT: 2650
Stbd= IDLE: 600 SLOW: 1500 CRUISE: 2300 WOT: 2800

VOLTS:
Port= IDLE: 12.5 SLOW: 13 CRUISE: 13.5 WOT: 13.5
Stbd= IDLE: 12.5 SLOW: 13 CRUISE: 13.5 WOT: 13.5.

WATER TEMP:
Port= IDLE: 160 SLOW: 175 CRUISE: 180 WOT: 180
Stbd= IDLE: 160 SLOW: 175 CRUISE: 180 WOT: 180


OIL PRESSURE:
Port= IDLE: 45 SLOW: 55 CRUISE: 60 WOT: 60
Stbd= IDLE: 45 SLOW: 55 CRUISE: 60 WOT: 60


Other observations: All above readings of instruments were within normal comparative range unless
otherwise specified. Temperatures shown are in fahrenheit.
RELATIVE TEMPERATURE READINGS
Risers:
Port engine:84 Port engine turbo: 264-228-194
Starboard engine: 89 Starboard engine turbo: Not taken (couldn't get to it)

Exhaust manifold:
Port engine: 167-164
Starboard engine: 167-166
The temperature readings and the differentials are within normal range.

Water pump:
Port engine: 78
Starboard engine: 76.

Transmission case:
Port engine: 125
Starboard engine: 127.

Stuffing box:
Port engine: 69
Starboard engine: 71
Stuffing box temperature reading is consistent with sea water temperature taken during sea trial.

Temperature comments: All temperature readings were conducted using a Robyi 600 Degree High
Temperature InfraRed laser sighted infrared thermometer. All above relative
temperatures are considered to be within normal levels and were obtained with
engine(s) RPM at 2800.

If I read your survey data correctly, I think you have answered the port side smoke and sooting more than the stbd side. If you WOT rpms on the port side is 2650, then you are overloaded. Both engines under your normal loading should turn up to 2800-2850. You can manage t he load thing in the short term by reducing your cruise rpms to 2650/2800 x 2400 = 2250-2275 rpm.

One other minor issue with the data you posted.......idle speeds on the 3116/3126 should be 750-775 rpm. Lower rpms than 700 increases wear on the valve train and injectors, plus, the engines can stall at idle speeds particularly when cold when you shift in /out of gear around a dock when the rpms are set too low. ANd my experience is they almost never stall, but if one quits it will be at the worst possible time.

Interesting about the idle RPMs, I'll check into that. Turning the big wheels, she already leaps forward when shifting into gear at idle, so I can only imagine what another 100+ RPMs will do. If it's best for the engines, I'll definitely look at doing it though.

I do know that the port side throttle needs adjusting, and I'm wondering if the WOT difference between port and starboard is because of that. When throttling up from idle, I have to advance the port side lever much quicker than stbd, so I'm wondering if the adjustment is limiting me from reaching WOT. The surveyor did mention that as well and said it could probably be adjusted out so they are equal. I need to look into that.

Thanks again for your advice, it's much appreciated. Sorry to the original poster for hijacking your thread!

Kevin

Kevin,

The torque from the Cat diesels is what causes the "jump" when shifting into gear vs. a gas setup. It's natural.

Yep, understood. Very torquey engines, my thought was that it would be more "jumpy" at the higher RPMs.