QSB 5.9 425 MISFIRE

[Robert Greig]

I have a question about a slight misfire/rough running 2012 QSB 5.9 425 HP, 1300 Hours. Data Plate info attached.
I have noticed that the fuel flow and boost was slightly higher on the PORT motor during cruise. After reading through the forums, it seemed as though it was negligible but listening and smelling over the transom you could hear a slight miss and smell stronger diesel exhaust odor on that side. No noticeable smoke. After hauling, winterizing, and running one final time without the impellors to purge out the exhaust, the misfire was more pronounced without the water to dampen out the sound. There are video’s attached of the port and starboard motors attached. Both at 1300 RPM. Some fuel flow and boost snap shots at various RPM’s attached also. Again, slightly higher on the PORT motor.
Possible clogged injector ??
I have had the boat for a season and a half here in the Northeast. 2012 35 Henriques Express. In regards to recent maintenance, I performed the aftercooler maintenance per Tony’s recommended procedure last winter. They were thankfully in good shape to begin with. Coming apart easily. Other than routine filter and zinc changes, no other significant items. Going though pre purchase sea trial pictures, it appears the condition was there so I don’t contribute the aftercooler maintenance to the issue.
Any thoughts ? Thank you.

Topic

[Robert Greig]

Thanks Tony ! I’m here to listen. This forum is great and you and your team are a wealth of knowledge.

Appreciate the feedback on the props and totally understand I’m working two issues unrelated to each other.

I’ll provide feedback when I get a tech with a computer to check out the injectors to diagnose the mis.

Thanks again………….Rob

[Tony Athens]

At this point, this is real simple if you want to listen………………

Take your props to a 1st class shop that knows ACME props.. Remove the equivalent of 2 full inches of pitch (nothing less) as you the need the equivalent of AT LEAST 200 RPM………………………… This has nothing to do with your “mis-fire”… You are close to “grossly” over propped for this engine as it needs to see the governed RPM of about 3080, and see it (EASY) at 96-98% load or less based on what you have posted..

I prefer 93-95% load at the governor as that is what this engine likes in real life field conditions. .. Remember, your engines are not in a controlled “test cell” environment on an EPA certified dyno…

It’s your call from here.. I have done my due diligence..

Tony

1 user thanked author for this post.

Robert Greig

[Robert Greig]

Finally got back to the boat after the holidays and New Year. Happy New Year !

Swapped actuators on the CR pumps but the problem did not follow. The miss still remains on the PORT motor. Will have to pursue a tech with a computer to check the injectors.

On another note, seeking advice on the overpropping situation. The previous posts have the photo’s of the fuel flow numbers but I summarized them here.

Keep in mind the higher FF on the PORT motor. I assume due to the miss.

RPM PORT FF STBD FF Kts
2200 11.2 10.8 22.6
2300 12.3 11.5 24
2400 12.8 12.4 26
2500 13.7 13.2
2600 14.8 14.4 28
2800 17.3 16.8

Two different WOT numbers below. The 1st set during the summer and another set during the run to haul out in December with 35 degree OAT.

P3000 / S3030 20.4 / 20.5 (100% LOAD Indicated) 32 Kts
P2920 / S2960 20.6 / 20.6 (100% LOAD Indicated)

Propellers are ACME 1103 (LH) & 1102 (RH). 22×27, .075″ Cup (Advertised).

The boat has an advertised displacement of 21000. I do not know the actual weight hanging on the slings. 35′ Henriques Express fishing boat.

All numbers based on 1/2 to 3/4 load.

Based on the Performance Curve it seems the FF is high at all points except WOT but it is also not making the governor speed RPM.

Anyway, open for suggestion. Let me know if I missed any info to assist with determining the best amount of pitch to take out.

Thank you, Rob

[Tony Athens]

Robert,

Exhaust is well done & safe..

You may have one,”not so right” injector or bad actuator on the CR pump… It would not be the 1st time.. You’ll need a tech with a plug-in computer to sort it out if it’s and injector.. You could swap actuators yourself……………………………..Pics on our web site..

..

Tony

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Robert Greig

[Robert Greig]

Some turbo pictures.

[Robert Greig]

Remaining pictures.

[Robert Greig]

Thanks for your reply Steve. I also agree on the over propped evaluation. I attached the 2500 fuel flow and boost numbers as well. Medium load. I’ve pulled the props already so open to suggestion on this issue as well. Props are ACME 22×27, 1.75″ shaft.
I have attached a bunch of pictures of the exhaust. Looks like it will be 2 posts to get all of them.
Thanks again. Let me know if more pics or details needed.

[Steve Lewis]

Robert,

Any chance you have detailed pictures of the engines? What does the exhaust configuration look like? also I took a look at the Performance Curve for the CPL 1860 5.9 425(see attached) and you are a touch over propped in the 2400 to 2600 range. Were you running a light load when you took those Vessel view pictures or max load? You might have other things to tweak in addition to what is causing the rough running of the port engine.

Steve

[Robert Greig]

Adding the Fuel Flow and Boost photo’s are they didn’t come through on the original post.

[Author]

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