RPM guage about 2000 off after boat back from repair shop

[gt2003]

2007 Tahoe Q6 with 4.3 L MPI. I had the gimbal bearing and impeller replaced and got the boat back last week. I took it out this weekend and it ran great. However, the speedometer didn't work for the first 2 or 3 trips but miraculously starting working yesterday. Also, the RPM gauge is reading about 3000 at idle. The motor sounds exactly as it did previously, not revved up or idling high, especially not 2000 or more RPM's high. The problem comes in when I go to speed up, the RPM guage shows about 6500 and the alarm starts beeping. Once I back off on the throttle just a bit and the RPM's on the gauge go down, the beep quits. Is there something they could have done while completing their repairs? I'm pretty sure he'll fix it with no complaints but if it's something simple then I'll attempt. Thanks

 

[alldodge]

2007 Tahoe Q6 with 4.3 L MPI. I had the gimbal bearing and impeller replaced and got the boat back last week. I took it out this weekend and it ran great. However, the speedometer didn't work for the first 2 or 3 trips but miraculously starting working yesterday. Also, the RPM gauge is reading about 3000 at idle. The motor sounds exactly as it did previously, not revved up or idling high, especially not 2000 or more RPM's high. The problem comes in when I go to speed up, the RPM guage shows about 6500 and the alarm starts beeping. Once I back off on the throttle just a bit and the RPM's on the gauge go down, the beep quits. Is there something they could have done while completing their repairs? I'm pretty sure he'll fix it with no complaints but if it's something simple then I'll attempt. Thanks

It's reading an over rev situation and the alarm is going off. Check the connectors for the engine main plug, back of tach, coil, grounds and ECM. The tach wire is gray/white.

 

[airshot]

I would take it back to the repair place and make them fix it. It worked fine when you took it in, should run proper when you get it back. You paid for a service make them complete it.

 

[gt2003]

I will be calling him first thing tomorrow morning. I spent way too much to not have it working perfectly!

 

[gt2003]

I took the boat in today. The rev limiter (I believe) had to be reset. He asked me to come to the shop so he could show me the process to reset it if this every happens again. He then started it up and it's running right where it always has at idle. He had the muffs on it and put it in gear and gave it a little throttle and backed it on down again to idle. It continued to work perfectly. Sounds like I'm back on the water this weekend. No charge for the "reset".

 

[achris]

????? I have a 2006 4.3MPI, and all the diagnostic tools, and I was a Merc dealer for a few years... No such thing as a 'rev limiter reset'. The tacho is driven directly off the ECU. One of the test functions available with the diagnostic software it to drive the tacho at a set revs, even without the engine running. I use that function to check the accuracy of the dash mounted analogue tachos. But there is no 'reset' of anything in the software, expect error codes...

What it sounds more like is that the ECU somehow lost sync. Just turning the batteries off and back on may have been your 'reset'....

Chris..........

 

[gt2003]

I'm sure I called it the wrong thing but here's what he did, he turned the key to the on position, waited for the fuel pump to stop, took the boat out of neutral and pushed it all the way forward and back to neutral 3 times. On the 4th time he did the same thing but stopped just short of putting it in neutral. He then turned the key to the off position and put the boat in neutral. I have no idea what it did but the tach works. It reminded me of resetting the "oil life" in a vehicle. Does that help any at all?

 

[achris]

... Does that help any at all?

Smoke and mirrors. He did nothing... As I said, I think just turning the key or the batteries off and then back on would have done the same thing.

 

[gt2003]

He mentioned the 50 amp fuse on top of the motor being tripped when he tried to start it, then said he reset it etc. I do appreciate your honesty though although it irks me a bit that he did that!

 

[achris]

That breaker being tripped would concern me. Why? Why did it trip, and is it likely to do the same again. Just one point on that breaker. It's the same as turning the batteries off. Being tripped removes power from the ECU...