changed all plugs and wires and boat still running 300-400 less rpm on left motor vs right? all the marinas and boat so called mechanics around here are morons. like to do things myself. but this im stuck on. any help would be great and i can take care of ya for your time.

If you can bring the beast down to Louisville I have the rinda unit with the connectors for 555 pcm. I had same issue with rpm's, was just a bad spark plug, looked real good after I took it out, but with new one in runs great again

the induced cylinder misfire test is what you need to do, has to be done at 2000 rpm's if my memory is right. Wont see the rpm drop at idle

Im in columbus, and have had experience with about all the shops. Where have you gone? I can point you in the right direction.

If you have not tried already, call Bluewater Marine out here in pataskala. Talk to a guy named Josh. He is a good guy and and knows his stuff. Only talk to him cause the rest of the guys there dont know as much.
740.927.2988

Tell him Sam sent you and he might hook you up.