Hello All,I am hoping I can get resolution for a two year project. (should not have taken that long but was trying to save money--not too successfully).
I have what was a 2002 496 Mag 375 hp engine (serial#OM084202). Purchased a new short block from a member on this site (thank you). Rebuilt the heads, put new injectors, coil packs, alternator, starter, raw water pump, fresh water pump, IAC, TPS, Risers, Manifolds, and more. Having read on the forums about the issue with the Cam position sensor being NLA and the conversion required. I decided that while the new engine was out of the boat, convert to the 2004+ cam position sensor and all that entailed. I used information from here and the link provided (Vortec 8100 8.1L Chevy GM Camshaft Position Sensor Guide - 496cid Cam Gear Sensors - Raylar Engineering)
After calling Mercruiser and talking to their tech and verifying the parts/conversion would work (I even provided a writeup on the parts and where to get them that the tech used)
I used the following parts for the conversion:

• Camshaft Position Sensor GM 12591720
• Sensor Adapter Pigtail Standard HP4240
• 2004+ Tall Sensor Timing Cover GM 12589846
• Timing Chain/Gear Set Cloyes C3222 -Summit Racing

After putting all the fluids and charging the batteries, the boat will crank but not start. It does start if you spray starter fluid down the throat. I had a marine mechanic come out. He was only able to get it to start and idle by spraying gas down the throat. He stated that the PCM was bad. The PCM thinks it is sending signal to the injectors but the injectors are not receiving signal. He said oil and fuel pressure look good. Since the PCM had been pulled and refurbished two years ago and was still under warranty, I pulled it and sent it in. Last Friday the tech called while running diagnostics on the PCM. He found no issues. He even ran a pin test on it. The PCM is firing the injectors as expected. We had a discussion and he noted that there was a code for the MAF and Cam position sensor. I brought up the conversion. He is pretty sure the wiring is not correct with the new cam position sensor and provided the old and new wire/pin positions on the new and old sensors. The new pig tail has all white wires and we replaced the old pig tail being careful to make sure the same plugs went to the same wire on the harness. Can anyone confirm the new plug/wire positions?
Below is my understanding of how the new sensor plugs are set up:

2002 Cam position Sensor (short)(Part No: 12575183)
Notch on top right
Left Male Plug - Ground - Black/pink wire
Center Male Plug - Signal - Purple wire
Right Male Plug - +5v - Grey wire

2004+ Cam position Sensor (long)(Part No:12591720)
Notch on top left
Left Male Plug - +5v - Grey wire
Center Male Plug - Ground - Black/Pink wire
Right Male Plug - Signal - Purple wire

If the above is correct then the pig tail is wired wrong. The right wire should be moved to center, center should be moved to left, and left moved to right.
Can anyone verify this?
Any help would be appreciated.

thank you,
wrath

I Believe the pics in this thread will help.

496 Position Sensors (Cam & Crank) Question

THANK YOU...THAT is EXACTLY what I needed!!!

such a simple reply to my long post!

Hello Wrath, I was wondering if you had to switch the wires, i am going through the same issue now, but my wires are not the same color, I am having similar issues though. My motor appears to be a early 2002 and I just purchased a long block with the upgraded cam sensor already installed, the long block manufacturer said to just shave the plug notch and install the same way. Let me know if you had to do anything else to accomplish the swap.