2001 Yamaha 225 ox66 Missing on cylinder(s)

[nautique95]

Hello, all. Here is the story. I have confirmed with a timing light the engine is missing on cylinder 6 but only below about 1500 rpms. It is especially noticeable under load. Once you hit a certain speed, it all sparks and runs perfectly. I exchanged the ECU (powerpack thing) from Cylinder 6 with the cylinder directly above it. The no-spark symptoms remained on cylinder 6 and did not follow the ECU. That would lead me to believe that the ECU is just fine and that something else is the culprit. I cleaned the grounding points that I could see and still same issue. Other cylinders could possibly be missing as well, but I believe it is just #6. Any guidance as to why it may be missing would be greatly appreciated. Thanks!
Jake

 

[nautique95]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

Okay, I've done a little research. Apparently the "big block" Yamaha ox66 engines are designed to drop two cylinders when below 1800rpms. Can anyone shed some light on why this should happen? Seems a little bizarre and even wasteful for it to not be running on all cylinders all the time. I don't understand why you'd ever want this. Is there anyway to disable or reverse this feature? Thanks.
Jake

 

[Capt Ken]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

Incorrect. They drop two cylinders when in neutral but pick them back up again when in gear. I believe it's number 3-4 that are dropped. You did not swap the ECU, you swapped the coil. The ECU is the big box on the rear. You need to use the diagnostic test light to see if there is any faults. Without the proper equipment to test the engine, you are chasing your tail.

 

[nautique95]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

Incorrect. They drop two cylinders when in neutral but pick them back up again when in gear. I believe it's number 3-4 that are dropped. You did not swap the ECU, you swapped the coil. The ECU is the big box on the rear. You need to use the diagnostic test light to see if there is any faults. Without the proper equipment to test the engine, you are chasing your tail.

Ken, thanks for the heads up on the ECU-coil mixup. I had heard it mentioned several different ways. It seems, however, with all of reading that I have done (a lot) that everyone agrees that up until 1800 rpms, this engine doesn't run on all cylinders. I wish it was as you mentioned it, but based upon all that I've read and the way my engine behaves, it is designed to run on 4-5 cylinders halfway through the acceleration stage. Something about the "power curve" or something.

Here's a question you might be able to help me with... where is the O2 sensor? I have read a lot of threads saying it is good to clean and inspect it regularly to avoid engine damage and that it may also be accentuating the rough running conditions I am experiencing. Any input on that?
Sorry for the long-winded post. Thanks,
Jake.

 

[jerryjerry05]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

Sent U a PM.
Also ask for a downloadable manual.
Make sure you have the serial#s and model#s.
There are some really good people on here, they will get you what you need.
Thanks again,Don!!

 

[Capt Ken]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

Hmmm, I bet you my Yamaha certification against the others opinions. That engine uses a shift switch to kill two cylinders while in neutral and re-engages them when shifted into gear. As for downloadable manuals. We dealers are forbidden to place online our manuals and Yamaha has gone so far as embedded our dealer number on the pages so they can be tracked back to the source.
You have a choice, take it to a dealer and have the diagnostics performed, or continue to spin your wheels.

 

[nautique95]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

Don, I appreciate that. I couldn't find the entire manual, but I will surf that site and see if I can find it. Ken, if you're certain that the engine is not supposed to miss on cylinders all the way to 1800 rpms, then I will continue pursuing the issue. I was hoping to diagnose as much as possible without going to the dealer. They wanted $100+- just to hook it up to a computer. :facepalm: I may take it up there just for my peace of mind. Anyway, here is what's left of the identification plate thing on the mount bracket and a picture of the whole engine for reference. If ya'll need any other pictures of stuff for reference, let me know.

 

[nautique95]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

Hmmm, I bet you my Yamaha certification against the others opinions. That engine uses a shift switch to kill two cylinders while in neutral and re-engages them when shifted into gear. As for downloadable manuals. We dealers are forbidden to place online our manuals and Yamaha has gone so far as embedded our dealer number on the pages so they can be tracked back to the source.
You have a choice, take it to a dealer and have the diagnostics performed, or continue to spin your wheels.

Ken, for your reference and mine, I looked up the "CCS" in the manual on "boatinfo.com". This information is located on page 3-58, 3-59.
There is a great write up about how these engines do not fire on certain cylinders. To your credit, it does make mention about a "shift cutoff switch", but it sounds like the engine's CCS feature is active both in neutral and in gear, but under different ramifications based upon whether it is in gear or not. If that isn't the case, and my engine is only supposed to activate CCS when in neutral, I think it's apparent that my shift sensor is malfunctioning and thinking that it is always in neutral. You may want to read through this and I'd love to hear your take on it. It really sounds to me like CCS operates both in neutral and in gear. Again, I could very well be wrong. The mechanic who worked on the engine here in Orlando also agreed that it should drop cylinders, but he didn't go into detail as to whether it changes in or out of gear.
Thanks, Jake.

 

[coolguy147]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

Do you know what the right cylinder number pattern is?

 

[99yam40]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

CCS should only cause a drop in cylinders when you shift, not when running normally.
Just to let the motor shift to or out of gear

 

[Capt Ken]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

It drops cylinder 3-4 when in neutral to get the rpm's down to a safe speed to shift. The system will also prevent the engine from rev'ing when the engine is in neutral. So if the engine will exceed approx 2000 rpm's, then the shift switch is not activated.

 

[nautique95]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

I haven't revved it that high in neutral before, so I'm not certain. Doesn't seem like there are any rev limitations, though. This motor sat without use in a fresh water lake for 12+ years and has practically no use. I just bought it and got it running again, so the shift switch could be messed up from sitting for so long, I suppose. Bottom line, what you're saying is that I should never experience a sluggish missing when trying to accelerate?
Thanks for all the help,
Jake.

 

[99yam40]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

If you do not think it is sparking properly, it would be a very good idea to follow the steps in the service manual for testing the ignition system using the proper equipment.
If you do not have the proper peak reading voltmeter for these ignition systems then get a DVA adapter and use a regular meter. They are not very expensive.
If all voltages are in spec then I would be looking at the fuel side of things, as it takes more fuel to run properly under load

 

[nautique95]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

If you do not think it is sparking properly, it would be a very good idea to follow the steps in the service manual for testing the ignition system using the proper equipment.
If you do not have the proper peak reading voltmeter for these ignition systems then get a DVA adapter and use a regular meter. They are not very expensive.
If all voltages are in spec then I would be looking at the fuel side of things, as it takes more fuel to run properly under load

It sounds like it is running as it should per what the manual says. It's a little irritating to listen to just because I'm not used to it. I have a multimeter, so I could run those tests like you were saying. Fuel system wise, the high pressure and low pressure pumps are brand new and the VST, Injectors, and hoses have all be replaced and cleaned. I can't imagine at this point there is a problem with the fuel delivery. Speaking of the fuel system, the manual talks about how the CCS shuts off the injectors to the cylinders that are not sparking. Would this not cause a loss of lubrication in said cylinders? Thanks, Jake

 

[99yam40]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

You need to test things to eliminate them for sure not just think they are not a problem

 

[coolguy147]

Re: 2001 Yamaha 225 ox66 Missing on cylinder(s)

It sounds like it is running as it should per what the manual says. It's a little irritating to listen to just because I'm not used to it. I have a multimeter, so I could run those tests like you were saying. Fuel system wise, the high pressure and low pressure pumps are brand new and the VST, Injectors, and hoses have all be replaced and cleaned. I can't imagine at this point there is a problem with the fuel delivery. Speaking of the fuel system, the manual talks about how the CCS shuts off the injectors to the cylinders that are not sparking. Would this not cause a loss of lubrication in said cylinders? Thanks, Jake

You will also need a DVA adapter to test the CDI equipment.