2000 7.4MPI knock code. Valvetrain?
 

I have the base model 330hp 7.4MPI with 400 hrs on it. MEFI 2. Have been getting the knock detect code for 2 years. My scanner shows a knock detect starting above 3000 rpm and its retarding my timing 3 to 6 degrees. I can't hear a knock. I had the engine out last year and installed new rear engine mounts and new coupler. One mount was bad and I thought my problem was solved but its not. I removed the drive today and ran the boat and scanner still shows knock starting at 3000 rpm. So something in the engine is causing this. Spark plugs look normal. Tried 93 octane gas and even added octane increaser but scanner still showed a knock.. I don't believe its detonation. I have checked both knock sensors via the manual and everything passed. The wiring is not close to the spark plug wires. My question for ya'll is do you think a valvetrain problem like loose rocker or collapsed lifter would be heard by the knock sensors? I don't hear anything odd in the valvetrain. Anytime I'm running above 3000rpm with the scanner connected I'm seeing the knock detect and the timing retard.

If it was a rocker or lifter you clearly would hear it at an idle without a doubt. It would be difficult for you to hear detonation with all the background noise running at 3000 rpm. If your system checks out as you claim I would think the sensor is doing its job and detecting a knock.

First thing I would do is validate base and total timing to insure it's correct. Check to see when full advance should come on your model then check against actual.

To much timing, junk fuel, carbon buildup hot spots can cause detonation. I would start with the total timing. If your scanner drops it 3 to 6 degrees what is the total advance at that point.

MEFI 2 is L29, and your getting a code 43

Have you tried disconnecting the knock sensors and see if you get a code 44 ?

Are the knock sensor wires running along side the plug wires? If so that's bad, need to have them perpendicular to the plug wires