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Go Back   SailNet Community > On Board > Gear & Maintenance > Ink black exhaust water - soot?
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Thread: Ink black exhaust water - soot? Reply to Thread
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Topic Review (Newest First)
05-09-2014 04:29 PM
gamayun
Re: Ink black exhaust water - soot?

I think the OP and the most recent poster are separate. The latest question had been resurrected on an old post....
05-09-2014 01:31 PM
jzk
Re: Ink black exhaust water - soot?

A quick search showed the max RPM of your engine to be 3600, and you are only able to get 3100. So why don't you start with the prop?

Quote:
Originally Posted by sandycohen View Post
Bubb - Sorry if I have gotten your bad side, not sure why you don't want to agree on anything that you seem to agree to.

For everyone else - an update:

Went out for a sail today.

First,- there is a foam air filter, and removing it had no impact on anything.

Second, prop is clear and unfouled, as is the bottom - I dove and checked - beautiful day to swim in Lake Pontchartrain.

The black exhaust water (I am going to stop calling it soot) starts to appear around 2300rpm, and gets progressively more black and less clear water as I go to 3100rpm. 2300rpm is about half throttle (based on the pedestal throttle control range, not the actual throttle arm on the engine, i didn't adjust or check that). I can get to 3100rpm at say 3/4 throttle and from there on engine speed will not go any higher nor does the engine sound any louder. Also, make speed seems to be about 2700rpm - additional engine speed doesn't make us go faster in the water that I can detect.

At 2200rpm I can move the boat around 5.5knots into a 10 knot headwind. That seems like an acceptable speed given the headwind.

Inside the sheltered harbor, I could only get to maybe 6.5 knots top with full engine speed - which is less than hull speed - more engine speed didn't make any difference.

Also I want to clarify that the stuff i am calling soot which is inky black water of varying concentrations in the exhaust, is suspended flaky particulate in the water (I took a sample) it isn't fine particles or liquid.

Also, even when I am at 2200 and the exhaust water is clear, if I take a sample of it there is some suspended particulate.

The amount of force ejecting the exhaust water doesn't seem to change tremendously as the color gets more and more black. This makes me think it isn't "cleaning" residue from the exhaust system, or it would always be the same. But my mechanical understanding of the exhaust system is nearly 0 so maybe I am wrong.

To where we left things yesterday, I am certainly happy with 5.5 knots cruising in a light headwind, as long as running at 2200rpm isn't doing me damage.

And, the biggest thing perhaps, as sawingknots pointed out wisely, is that my tach could be wrong! But, my idle shows about 800 to 900 which seems right. And, would this explain having 1/4 of my throttle travel show no change in engine speed?

I welcome everyones comments. I did not open the elbow yet, and I certainly can, but wanted to share this info first.

Thanks to all.
05-09-2014 11:31 AM
christian.hess
Re: Ink black exhaust water - soot?

Quote:
Originally Posted by casey1999 View Post
I have a 1980 Yanmar 3gmd. I believe same as the OP's engine but 3 cylinder. I think my boat is also over proped as if I run at anything over 2500 rpm the engine just goes faster but boat is already at hull speed so goes no faster. I do not blow black smoke, by the exhaust does become more gray and the engine seems to start running hotter and seems stressed.

I have also heard the yanmars like to run at 80% max rpm. But to me, that is really straining the engine. I know what Mack Boring and even the Yanmar manual says, but it just seems to be straining the engine, and higher rpm mean more wear on moving parts. I do however run the engine in neutral for 30 seconds or so at full rpm prior to shutting down- to blow out the carbon as the Yanmar manual says you should do.

I believe my engine has been run this way for the past 34 years and does not burn oil or have low compression. Exhaust is clear.

I would just run your engine at the lower rpm if that is what your boat is happy with.

The I also agree with the OP's PO- it is difficult to get the perfect prop specs considering the effects of wind and waves will have on the load the engine will see.

As far as the engine oil dip stick, sounds to me the your range is too wide, I would go to a yanmar supply and compare what they would have for your engine

my 2gm loved to run at 2600-2800rpm

yeah a smaller boat but was higher than most guys like to cruise at

for what its worth I do beleive that yanmars like to be loaded up a bit more

its something I have heard over and over again many places around...

also propping correctly should be done on a new or at least rebuilt engine since with a very old tired engine or simply run long hours wise you might be diagnosing and fixing symptoms caused by other problems and issues.

for example in this case it seemed to be the prop all along, but a tired engine with badly sealing or worn rings, and sticky valves or bad seating valves will exhibit the same symptoms

not to mention the getting hotter issue which can be caused by improperly seating valves and carbon buildup

pistons that have a bunch of crap on the domes will create a fake compression and require better cleaner fuel in general terms...so if you find that all of a sudden(it takes years but you dont notice since performance degradation is gradual) you start getting hotter and billowing smoke and soot out the exhaust

BUT you have confirmed your exhaust, elbows, water lifts, manifold and all are clean and clear and not clogged up

that means you have to clean up carbon buildup and or start dooing at least a partial rebuild

anywhere from the fuel system to injectors to pumps

or valves, combustion chamber, pistons etc...

tolerances will get bigger as the engine wears

so a QUICK test is to add something like zddp additive by stp...and use a nice thicker oil than recomended

like someone else mentioned if this improves and decreases soot and exhaust smoke and smells, it will also quiet down the engine, it simply means your engine is a but tired in general terms and simply needs a rebuild



if you dont feel like doing this there are ways to clean up a bit without tearing apart but they arent always succesfull..

for example a high doseage in a full clean tank of fuel of SEAFOAM, under load at the dock or towing something for example, many times over can help to loosen deposits and stuff inside the engine

however the only real way of getting an engine back to specs is to get tolerances and parts back in new or original shape

bearings, pistons, rings, shims, valves, seats, flat surfaces, gaskets, o rings....etc etc etc...
05-09-2014 10:51 AM
jzk
Re: Ink black exhaust water - soot?

Forgive me if this has already been answered, but what is the max RPMs of your engine? Can you hit that at full throttle?

The tone of the correspondence from the OP sounds like he knows it was a pitch problem.
05-09-2014 09:44 AM
deniswithane
Re: Ink black exhaust water - soot?

Not easy to see the diff without looking at the numbers, which were rubbed off! I am so thrilled as this has cnot cost me a fortune and all the upheaveal again after a 1 1/2 yr warranty cleaim fight with VP over a faulty design on a sail drive fitting my engine which blew the crank case seal after failing for the 3rd time!

I am so happy!!!!
05-08-2014 07:22 PM
casey1999
Re: Ink black exhaust water - soot?

I have a 1980 Yanmar 3gmd. I believe same as the OP's engine but 3 cylinder. I think my boat is also over proped as if I run at anything over 2500 rpm the engine just goes faster but boat is already at hull speed so goes no faster. I do not blow black smoke, by the exhaust does become more gray and the engine seems to start running hotter and seems stressed.

I have also heard the yanmars like to run at 80% max rpm. But to me, that is really straining the engine. I know what Mack Boring and even the Yanmar manual says, but it just seems to be straining the engine, and higher rpm mean more wear on moving parts. I do however run the engine in neutral for 30 seconds or so at full rpm prior to shutting down- to blow out the carbon as the Yanmar manual says you should do.

I believe my engine has been run this way for the past 34 years and does not burn oil or have low compression. Exhaust is clear.

I would just run your engine at the lower rpm if that is what your boat is happy with.

The I also agree with the OP's PO- it is difficult to get the perfect prop specs considering the effects of wind and waves will have on the load the engine will see.

As far as the engine oil dip stick, sounds to me the your range is too wide, I would go to a yanmar supply and compare what they would have for your engine
05-08-2014 06:50 PM
zeehag
Re: Ink black exhaust water - soot?

my cute lil yannie 2qm20h makes the sickest looking stream of black when i havent used it in a while and then use boat. dealer distributor sed it was fine. he also overhauled it less than 150 hours ago when i bought the boat.
when my perkins did did that, it was past time for major work. (in
progress)
05-08-2014 12:02 PM
christian.hess
Re: Ink black exhaust water - soot?

darn must of been quite the difference in pitch...

congrats!
05-08-2014 06:55 AM
deniswithane
Re: Ink black exhaust water - soot?

I am so happy

As I have sorted out my problem on the one engine that the mech said was burnt out oil rings, etc. !!!!

I took off the prop on this port engine (which was a spare as such but was supposed to be identical to both the originals!) and put the old original re-painted one back on and HEY PRESTO, NO MORE BLACK SOOT under load!

So it was the prop pitch after all.

Thank you so much to everyone who pointed me in the correct direction - I have just joined this forum and what amazing feedback I got from all of you, without your input I would never have realised that and would have wasted good money on a mech who did not know much more than me !

Thanks again
Denise
05-05-2014 03:49 PM
deniswithane
Re: Ink black exhaust water - soot?

Elbows new, will check pipes - only 725 hours on this engine and running very cool in hot water of the Carib.
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