i installed a used marine power MPFI 350 in my boat. at first it turned 3700 and each and every time i use it it seems to lose some RPM. last weekend i could only get 3400 out of it. it seems slightly sluggish but runs great. fuel economy seems poor too. im thinking first i need to do some general maintenance like plugs, wires and distributor.
with the poor fuel economy im wondering if maybe i need to reset the TPS because it is in a different boat and i had to change the linkage a bit. it seems to start pretty easy and no hesitations. just when i throttle down it seems a bit sluggish.
i have already checked to make sure the throttle blade is opening 100% and it is so that should rule out cable position.

3700 is about 1300 RPM's too low and certainly not good for the motor. What was the old motor and what did it turn the current prop to for RPM? Also, what kind of boat is this in?

3700 rpm at full throttle is lugging the engine and that alone overtime will cause engine damage. I would compression test and possible leakdown test.

Also I would check your fuel pressure readings along with running the engine on a portable gas supply with new fuel line hooked to your fuel inlet engine side.

Also what kind of shape is your prop and pitch - what size boat and brand / model ? I would start there first then move on to the mechanical stuff and testing.

Is your hull bottom very clean and or any damage

this is how we normally run our motors. cruising RPM is around 3000 and depending on impeller 4000 is WOT.

the exceptions are the LSAs which we turn impellers to about 4500 give or take.

boat is a custom weld.

no ideas? MP thought i might check FP and i plan on doing that.