EFI- you can't just replace a TPI without adjusting it with a special test harness and digital VOM... A faulty head temp sensor can increase fuel consumption up to 40% except at WOT speeds. You can remove it (tan wires at top of head (s), test it with a meter by placing it in ice water and looking for resistance change. Air temp sensor (located above TPI), can also be checked that way. Also check the VST (vapor separator), 'bleedline fuel filter'. It's the tiny one (later models may not have it). If plugged up, crankcase puddled fuel won't get recycled into the vst . Note whether or not you are seeing a rainbow-like oil slick around your boat while fishing, lol.