Greetings,

I have a 1998 Carver 400 CMY with twin Mercruiser 7.4 MPI engines, MEFI-2. I've had the boat for about 6 months. Starting with the sea trial, it was noted that the Starboard engine would not rev to much more than 3,200 RPM under load. The Port revs freely to about 4,400. Starboard will hit 4,400 in neutral. The engine isn't showing any fault codes, my engine guy is using Rinda's Diacom software. Props, standoff bearings, shafts all check out fine.

Engines were checked out, and the starboard did have one cylinder with low compression. I got a purchase allowance, and both engines have new manifolds and risers, and the starboard has new OEM heads. Compression good all around. 3,200 rpm max on Starboard is still there.

I also note that fuel consumption on the starboard engine is about 30% higher than the port engine. 3,200 is a good cruising speed, and I'd probably leave things along, but the fuel consumption is a problem.

Based on my internet research, it's likely a sensor issue. 3,200 is the 'safe' rpm for limp home mode, and there are a few posts out there with similar symptoms, but often end before a conclusion is published.

My question to the group: anyone heard of similar problems, and a resolution? I think the next step for me is to swap sensors between the engines, and see if the problem moves to Port, thereby identifying the problem sensor.

Thanks!

John Magrann