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GT40- No Top End Power

minasianj

New member
Hello,
My 1994 GT 40 (fuel injection/EFI) is not getting full power at WOT. At WOT we are getting 4000 RPM rather than the usual 4600-4800. Listed below is a timeline of the problems development.


1) Initially at WOT the boat would top out at 4000 RPM and intermittently surge to 4800 full power. I added octane booster and a fuel system cleaner with no impact. Some days the surging was more prevalent than others, and at time the boat would run at full power for significant periods of time.


2) I replaced 8 spark plugs (.045 gap) and discovered one spark plug had a significant stem crack with carbon residue around the stem. Some individuals had previously mentioned they smelled fuel vapor during operation so this made sense. During the water test with 8 new spark plugs I received full power 4800 RPM at WOT with no surging. We thought the problem was solved, and maybe it was.


3) After the water test with 8 new spark plugs described above the low-pressure fuel pump ceased operating when the ignition was turned on. I replaced the relay and the pump has kicked on every time sense, but since the relay replacement the boat is back to 4000 rpm at WOT except now there is NO surging to full power, it tops out at 4000 and stays there.


4) performed a spark plug test and every plug had spark while cranking.


Any suggestions or ideas are appreciated.
Thanks,
Jackson Minasian
 
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