350 Mag MPI Horizon Won't Go Over 2500 RPM In Gear

I'm new here and looking for a little help. I have a new to me boat with 2 2003 350 Mag MPI Horizon inboards. When I first got it in June both engines ran fine all the way to full throttle . Since then the port engine has been a huge headche. The distributor failed csusing a misfire which bent a valve. We had he heads rebuilt and replaced the distirbitor, cap and rotor. Compresion is good on all cylinders and fuel pressure is 40 psi at the dock. New fuel filters too. It runs fine in neutral but in gear it's like it hits a wall at 2500 rpm. As far as I can tell it's not in guardian mode because it has the smartcraft guages and they tell you when the engine goes into guardian mode right? I was thinking it was a fouled bottom on the boat but wouldn't that stop both engines? Anyway, we're stumped right now. Anyone got any ideas?

I've read another case of this happening where the Crank Position Sensor would intermittently lose signal over 2500rpm, but wouldn't store a code in the older MPI computers. Mercruiser had to get involved to diagnose the problem using their portable engine dyno since it could only be diagnosed under load with a scanner hooked up monitoring the sensor values. Poor guy spent a lot of money diagnosing the problem too:

https://www.baylinerownersclub.org/...mercruiser-5-0l-mpi-bravo-3-gctid815795/page5

Does your engine have a gen2 or gen3 fuel cooler? What is the fuel pressure while running the engine up in gear?

40psi at the dock is a little higher than it should be if your gauge is accurate.

I don’t think it’s a gen 2 or 3 fuel cooler. It’s the one that has the boost pump on the right side of the engine with the screw on filter and the main pump on the other side . The crank position sensor would make sense. It’s gotta be fuel or timing or drag I would think because the compression is good and it will run normally out of gear. I haven’t tested the fuel pressure with it in gear yet.

It's a gen2 fuel cooler. The high pressure pump is mounted under the port engine mount.

Fuel pressure in gear running down the lake/bay is what we need.

When the heads were reinstalled how were the lifters adjusted. Anything more than 1/2 turn is too much and will cause issues.

I understand.The valves are fine I think.ill check them the next time I’m there. I won’t be able to run it again until this weekend. I’ll take the gauge with me and see what happens.

Sorry I’m just now updating this. So here’s the verdict. It’s done for. It’s a bad ecm. On top of that a wrist pin let go. Distributor fuel pumps injectors all good. So time for a new short block and ecm. Basically doing a repower in pieces. Any suggestions on good marine short block manufacturers?

Before you drop $$$ on an ECM....Find one to test with...