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Ted G.
Ted G., Rigger, Diagnostician
Category: Boat
Satisfied Customers: 6159
Experience:  40 years boating, Safe boating instruct., Offshore Race promoter, Failure Analysis, Expert Witness
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2005 mercury 60hp efi bigfoot. When running at around 35 min

Customer Question

2005 mercury 60hp efi bigfoot. When running at around 35 min cylinder 2 shuts down ocassionally comes back,but stays down after 45 min of use. Changed all coils plugs wires, new plugs, completely cleaned fuel vst tank, new fuel line and tanks, runs perfect until about 30 mins then it loses #2.
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.

Hello my name is ***** ***** am I speaking with?

How are you determining the #2 cylinder is shutting down?

Does the alarm system work on the engine, does it beep every time you start it up?

Customer: replied 2 years ago.
This is Joe. I have unplugged the spark plug wire from #2 when the motor is acting up. When I pull any of the other wires the motor runs worse. No change when I pulled #2. I had a tech plug this into his laptop and everything is perfect. I get the beep every time I turn the key.
Customer: replied 2 years ago.
Tech did tell me his laptop read #2 as well before I installed all new coil packs.
Expert:  Jason replied 2 years ago.

Have you done a spark output test on #2 with a spark tested to check and see if it was actually loosing spark?

Expert:  Jason replied 2 years ago.

(vs an injector not firing)

Customer: replied 2 years ago.
the spark is definitely firing. Before I changed all the coil packs I just changed #2. Then after 35 min the issue was #3 so I just changed them all and now it's back at number 2. Why would it work great for 35 min then have issues?
Expert:  Jason replied 2 years ago.

What i'm asking is did you check for spark when the engine was acting up and running poorly, which means did you check it out on the water? Or did you check it when the engine was on land and running fine?

Customer: replied 2 years ago.
Checked it out on the water.
Expert:  Jason replied 2 years ago.

And it has spark on #2 when out on the water?

Expert:  Jason replied 2 years ago.

I just want to make sure.

Customer: replied 2 years ago.
Expert:  Jason replied 2 years ago.

It's possible you actually have a failing injector. You can do this 2 ways. Either move the #2 injector to another cylinder and see if the problem follows the injector or not. Which would actually be the easier of the 2 ways to go. Or, run the boat until it acts up, and then disconnect the injector and measure it's resistance with a multimeter. Spec is 10 to 13 ohms. If it is high or low that would confirm a bad injector. Does that make sense?

Customer: replied 2 years ago.
I I did that and it still comes up number 2
Customer: replied 2 years ago.
This is a difficult one I've been told from the text
Expert:  Ted G. replied 2 years ago.

Hi, let me see if I can help. With the engine running properly at idle, back probe the injector connection with a high impedance voltmeter and take a reading. There is no spec for it but use that reading as your baseline. Now when the engine fails do the same test. I suspect the injector driver for #2 in the ECU is failing. You will likely see no voltage or a much lower reading when the engine fails if that is the case.

Customer: replied 2 years ago.
I'll try that today. Sounds like the driver if so is that a costly fix. New ecm or just a reflash?
Expert:  Ted G. replied 2 years ago.

It would need the ECM either replaced or repaired at a place like CDI