@help starboard engine not reaching max rpms

[txav8r]

Hip hip hooray!

 

[rgibson20]

Thank you guys for this thread. I recently had the exact same problem. Went ahead and changed the plugs and it was a quick and easy fix.

 

[RPeoples]

@HELP maiden voyage today and the starboard engine won't get over 6500 rpm while the port gets over 8000. Anyone?

This is the exact same issue I am having. I don't have the answer but here is what I have eliminated using Yamaha diagonstic software and the service manual.
1. No current logged errors in ECU showing issues. (timing and or sensor failure)
2. Throttle mechanism and throttle body are currently in spec with service manual test
3. Manifold temp & pressure sensor works fine
4. Swapped ECU with starboard engine and no change
5. Without loading the engine and jet can perform just as the starboard engine
6. Plugs are black from rich mixture, which is why I believe it is limited in RPM under loading
7. I have confirmed and eliminated any air intake issues

I only have a few other items left to check.
1. Fuel pressure check, but I believe that is is not overpressuring the rail
2. Swap the cam sensor to see if that could cause a slight timing issue
3. Exhaust temp switch, could that cause an issue with fuel mixture?
4. If the timing chain is off by one(1) touth would it throw an error in the ECU?

 

[RPeoples]

This is the exact same issue I am having. I don't have the answer but here is what I have eliminated using Yamaha diagonstic software and the service manual.
1. No current logged errors in ECU showing issues. (timing and or sensor failure)
2. Throttle mechanism and throttle body are currently in spec with service manual test
3. Manifold temp & pressure sensor works fine
4. Swapped ECU with starboard engine and no change
5. Without loading the engine and jet can perform just as the starboard engine
6. Plugs are black from rich mixture, which is why I believe it is limited in RPM under loading
7. I have confirmed and eliminated any air intake issues

I only have a few other items left to check.
1. Fuel pressure check, but I believe that is is not overpressuring the rail
2. Swap the cam sensor to see if that could cause a slight timing issue
3. Exhaust temp switch, could that cause an issue with fuel mixture?
4. If the timing chain is off by one(1) tooth would it throw an error in the ECU?

Also, I forgot to mention the very first thing that I did was to change the spark plugs, but to no effect.

 

[Rob 212ss]

RPeoples did you find an answer, I have one motor doing, the same thing and am troubleshooting similarly.

 

[RPeoples]

I have the same issue that is not caused by plugs but caused by burning too rich, which is only on the port side engine.
Just to be clear on this issue let me reinstate the problem. Starboard will go up to about 8500 RPM and the port will only reach about 7100 RPMs.
I have not swapped the RPM gages to see if they may possibly be out of calibration.

I do have the diagnostic software and it does not record any faults or errors. All cylinders are firing and I have replaced the injectors as well but to no avail. ALL of the input sensors have been swapped from the starboard to port one at a time in an effort to identify the issue, but unsuccessfully.
The plugs on the port side are black with soot after each outing. The underside of the platform on the port side is marked with black exhaust stains.

I have performed compression tests so it's not a mechanical issue inside the motor. I removed the original air filters and replaced them with K&N filters so it's not an air issue. The fuel pumps have been swapped and it does not make any difference. So the fuel delivery is not a problem. When I disengage the pump without a load the engine will rev up to high RPMs just like starboard, but when under a load it will not.....Since I have tried everything I am thinking that the bearing housing on the engine compartment wall or the end bearing in on the turbine could possibly by causing too much loading??

I have engaged with several mechanics and not able to pin-point the issue to the motor. One guy mentioned to me that if someone worked on the motor, and I believe they have, and if they did not use all Yamaha OEM part that he has witness limitations similar to this. If you all have any suggestions please let me know as I am running out of bullets.

 

[buckbuck]

@RPeoples Did you swap the ECU's? The issues you are describing suggest to me the ECU is holding one or more injectors open. This is a known issue on the high output MR-1 engines.