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Sync-N-Cruise RPM not matched

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brock71

New member
I have 2007 8.1L Crusaders with Sync-N-Cruise and a Murphy display panel. My problem is the slave engine lags about 100 RPM lower than the master. I first noticed the drone/beat frequency noise then check RPM. Tried it under load up to 3400 RPM and in neutral at the dock. Same result in both cases.

Engines running smooth. Changed fuel filter. Spark plugs have about 15 hrs on them. Checked for loose plug wires. I did not run un-sync'd at full RPM under load. Should try that.

The slave has an extra accessory that is belt driven and provides more load on that engine. It is a hydraulic pump. When I took the belt off the pump then the Sync-N-Cruise worked properly. RPMs were matched. So it looks like the extra load slows the slave down. I don't recall this much mismatch in RPM ever before. Seems nothing has changed.

Does the Sync-N-Cruise look at only throttle position or does it see real RPM?

Are there any sensors involved that could affect this?

Any parameters to look at on the Murphy?

Thanks for your help.

 
When twin engines are not in sync, we can sometimes notice what's called a "harmonic vibration". I do not know the answer to your question, but would ask if you are sensing harmonic vibrations due to the 100 RPM difference?

We can hear similar harmonics when a truck (with loud exhaust) is near us in city traffic. If the truck's engine is not creating the same frequency as our vehicle's engine is, we can sense them.

I did a Google search and came up with these:

http://www.marinegate.com/pdf files/Sync_Cruz.pdf

http://www.marineengine.com/boat-forum/showthread.php?83701-Crusader-engine-synchronizer


https://www.google.com/search?ei=2s...7......0....1..gws-wiz.......0i71.rGLsrEhDbME
 
The 2007's should have the CANBUS ECU's with the digital throttle controls....and my understanding is that the cruise-n-sync looks at the measured RPM data to make the adjustments. If your Murphy's will read all of the data provided by the ECU's, I'd suggest starting with the digital throttle control parameters.....
 
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