Port 502 MPI just quites
 

I have a 1997 Baja Boss 302 with twin 502 MPIs in it. When I first start it up they run great at any rpm range. After some heat builds up the port engine starts to run rough and then dies. I can smell gas and hear my fuel pump but it will not start. I took it to Mercruiser shop and they could not get the ECM to show any info on the port engine. The ECM on the starboard engine gave all the info about itself. They switched the ECMs between the two engines and the same ECM that would not show info while on the port side would show info about the starboard engine but the one put over on the port engine would now not show the info for it. Does anyone have a similar problem with a fix or anyone know anything that might help me? I need help in a big way.

I would guess your performance problem is ignition related if you can smell unburned fuel being expelled out the exhaust.

On the issue of not being able to communicate with one engine, it sounds like you may have an engine that was made before elimination of Power Reduction Mode in mid-year 1997. All twin engine installations made before that time were supposed to have a data link harness that connects the two engines data stream. This was to help prevent loss of control of the boat if one engine went into Power Reduction Mode. With the link harness, if one engine goes into Power Reduction Mode, they both do.

To explain further, there is a single wire data link "harness" that is connected to the three pin Master/Slave connector at the back of both engines and on one end of the harness the other two pins of the three pin connector are jumped which forces that engine to be the "Slave" engine. The "Master" engine is almost always the starboard engine. What your shop needs to do is connect their scan tool to the Master (Starboard) engine and connect in twin engine mode, then they will see data from both engines.

Thanks for that info. I will call my shop on Monday and ask if they did that.