2004 Mercury XR6 150 high end stutter - OT932824

[78dave]

Ok, I am struggling to figure out my issue. It started with an across the entire throttle range a miss and just ran poorly. New fuel pump diaphragm did not change any thing so I re-built all three carbs and new fuel lines. Still did not fix it. In the end it was the control module. That was replaced and it ran perfect once again. I fished for three days no problems and then took the wife for a ride and as I came up to full throttle it started stuttering (4200 RPMs). At rpm's below 4200 it ran just fine, but push the throttle to full and it stutters. I took a video for my mechanic to see and he immediately said you need to replace the voltage regulators. I replaced both.

I have the same issue still - it stutters at 4200 rpms. Runs fine out of the hole and up to 4200 rpms. Then it stutters and no more power after that. What to do?

Thanks for any thoughts.

[JOE54]

need to determine if its fuel or fire

[78dave]

Well past your comment - not a fuel issue. I thought I would update you on what my mechanic suggested. He is concerned after watching my video that the rev-limiter circuitry is reacting to perhaps a shorted out tach. In fact I have replaced this tach once. He also said it is possible one of several sensors could be bad and triggering the same thing rev-limit. So first I will put the boat in and disconnect the grey wire from the voltage regulator going to the tach to see if that corrects the situation. Then I will unplug the flat plug at the control module that receives data from the oil and heat sensors and try that to see if it still being rev limited. I'll let you know.

[JOE54]

possible bad controller [rev limit circuit]

[78dave]

If I follow through and unplug the items I noted then that should take me back to the co0ntrol module. Just as a side note, I never see a wiring diagram that shows the CM, instead I see switch boxes

[JOE54]

dilly dilly,more info in v6 2.5L also