my buddy has a 42 fountain with twin 575 sci.port motor burned 20 more gallons of fuel than starboard motor.swim deck is all black on 1 side and engine loads up.any suggestions on what to look for?

Float level. Needle and seat leaking. Blown Power Valve.

Not sure what it is but it's not the float since there's no carb.

could be a stuck injector or a bad/ out of adjustment tps

they are throttle body injection,do you know what the t.p.s volts are supposed to be

Possibly a bad coolant temp sensor ???

( ecm thinks engine is "cold", dumps more fuel)

Pressure regulator it has an over flow tube that dumps in the throttle body

TPS voltage should be .59 and base IAC should be 11 - 19.
CHECK the timing using the proper method too.

I had a map sensor go bad on my 575sci last yr, was way rich at idle/part throttle but by the time I nursed it to 3500 it would drink what it was pouring in. Merc wanted 150ish, it's a GM part, 93 buick riviera 3.8 SC if I remeber right, 1/3 the price. Fixed my issue.

I'm pretty sure the tps should be .5 at idle and 4.7ish at wot, not sure what the iac count should be.

If one injector is stuck it should be obviuous watching it while idling. just remove the spark arrestor and they are in plain sight

these are the correct #s