I've got a 1998 Baja Boss 232 w/ the 454 mag MPI (385hp). Taking off engine will only rev to about 2600 rpm and is laboring especially with any load in the boat. Takes quite a while to get on plane. Once on plane and trimmed up I'm only getting 4000 rpms and around 48 mph. I still have throttle left but it does nothing. I checked and throttle body is opening completely. Prop is a Mirage plus 23p. New plugs, wires and fuel filter didn't help the problem. Just looking for advice on where to look next. Thanks

Sounds like your down on power big time.

Easy: Scan for codes & fix if any are there. Check the timing.

Next: Compression test, and leak down test next. Sounds like you have a couple clyinders low.

For referance Steve's 232 islander with 7.4 MPI (310 or 320 HP) he runs a 23 mirage plus also. 53-55 with a load. 60 MPH with light load.

Ditto

Any chance it might be going into "limp mode" because of a sensor reading?

Limp mode or injectors boogered up, causing lean condition.

Fixed! After not finding anything checking the fuel system I noticed on the parts diagram that there should be a spacer holding the thermostat up in the housing. Apparently the guy I bought it from had it winterized and whoever did it left it out. Took it out today after installing it and ran much better out of the hole all the way up to the mid 60s

I would have to say that your water temp was low and the coolant temp sensor was reading cold start kind of like a choke that was stuck closed on a carb app hence the ecm was telling the fuel injectors to dump more fuel (stay open longer - wider pulse width). Pulse width of an injector is the time it stays open to flow fuel. Anyways thanks for the update. I wish everyone did that. A scan should of gave you out of spec of the coolant temp sensor.