Smoking 6bta

[David Wesner]

Keel cooled JWAC 6BTA, CPL CPL953. Tach is 200 high. Unknown hours WOT is 2750 RPM photo tach. 32’Novi, 17,000lbs,2.57:1 gear with a 23×26 high cup wheel.

After 1300 RPM she starts smoking, black to brown. The engine is not the easiest to start in the cold, I crank it without fuel for 10-20 seconds then start and she will start 20-30F. Spring/Summer temps it has no problem starting. Blowby appears fine, no test done to measure…but it doesn’t look bad.

Aftercooler and injection pump do look like they have been worked on at some time. I believe this engine did ingest an air filter due to an exhaust leak at one time. Exhaust leak has been corrected and I have installed a filter minder which reads fine. I also checked the air manifold with a vacuum gauge to see if there was any restriction in the aftercooler. Nothing notable observed. I also have run with the engine hatch off to verify air supply not being an issue.

At first I thought I might be overpropped. But, with some reading I understand this engine to be a lower boost at low to mid range and high EGTs are common.

How would you attack this issue? My thoughts tend to go looking at the injector pump settings and timing. I do need another wheel and I would significantly reduce pitch. The main reason being I cannot use the top part of the RPM range anyway because of the displacement hull and the engine would be happier also.

Topic

[David Wesner]

So, I have had time to remove the after cooler and it did not look as gunk’d up as I was expecting. Found a ding in one of the coolant tubes that may be a crack/leak. Contemplating replacement over ultrasonic cleaning. I did do a simple green hot bath overnight and a brake clean of the fins without too much coming out. I am still reluctant on believe that this is the cause of the smoke. Just expected it to be dirtier.

[David Wesner]

That was a concern. And I’m not surprised about your thoughts. Curious why I didn’t see anything on the vacuum gauge before. It must not have been sensitive enough, or the level of restriction was below what I thought I was attempting to measure.

Thanks for the advice.

[Tony Athens]

Two things………..

1) ———— You tach is way off ( maybe 300+ RPM).. But that is not the issue..

2) ————- Either BUY a new aftercooler, or remove yours and have it cleaned professionally————–DALLAS COOLERS in Texas is where we sent them………….No place better…………. I believe a new genuine Cummins one is about $600 or less…

Your engine is not getting air..

Tony

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EMF

[Philip]

Understood the JWAC resolves the salt water side, but the air side can easily be clogged up with oil, dirt, gummy stuff, sludge, exhaust, who knows what…. Even JWAC need a cleaning, especially since you mention the filter was possibly eaten due to an exhaust leak.

Phil

[David Wesner]

Thanks Philip,

The after cooler is not a SWAC it is a JWAC, no sea water running through it and no o rings or grease needed.

D

[Philip]

Turbo looks ok to me.

Time to remove aftercooler, clean, pressure test, assemble with new o rings and lots of grease, pressure test and re install….

Phil

[David Wesner]

more turbo

[David Wesner]

turbo pics

[David Wesner]

speed vs RPM attached

[David Wesner]

Tony,

High idle is 3400RPM on the gauge and with the 200 error it should be 3200. I really need a second hand in getting a lot of the data. It’s on the list of things to do.

Engine has a dry stack. The exhaust elbow is fine.

Speed at 1300 RPM is 6.5 to 6.8 knots. Close to hull speed.

Where do you go for ultrasonic cleaning services? Is there an industry that uses this regularly.

The engine seems to behave as expected with the prop calculators. Not sluggish at all. Only concern is the black exhaust.

I will work on getting the data needed as you requested.

[Tony Athens]

David,

This is what you need to do in this order (regardless of what you think you have measured). Understand, this engine is not not less than 28 years old and been in a boat ( salt water environment) ever since new..

1) Remove the aftercooler ans have it professional cleaned & inspected.. They need to be cleaned ultrasonically to be done right.

2) Remove the exhaust riser/ wet elbow or ??. Then take a good picture inside the exhaust outlet–I want to “see” inside. Clear & in-focus like the pics I have posted on this web site

3) Your WOT RPM–Is that loaded as you use the boat or No-load in neutral?

4) What is the vessel speed at 1300 RPM? What is the vessel speed at 1800, 2000, 2100, 2400, and 2600 RPM..

5) stand back 3-10 ft and take/post pictures of the entire engine –Be sure I see the exhaust system, , turbo, etc..

Let’s start with that.

Tony

[Author]

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