GT 40 Acceleration Problem at Higher RPM

[JayG80]

Boat Specs: Ski Nautique Ltd 2002 with GT40, Perfect Pass, 201 hours. New fuel filter in May at 150 hours. Bought boat in January. Idles smoothly. Temp & Oil Pressure gauges read normal

The boat has been problem free up until this morning when on 2 attempts, it could not get my skier up past 30 mph. .

Dropped off my skier and turned off the perfect pass. The boat will gradually accelerate up past 34 mph. If you start from a stop and give it a lot of gas then the engine won’t get up past 30 mph. Won’t get to top speed if you are cruising at 25 mph and give it a sudden throttle instead of gradual throttle.

I cleaned the butterfly, throttle body & spark arrestor with throttle body spray cleaner. Replaced the spark plugs and they look good for 200 hours. Sand rotor tip and cap contacts.

No water in oil or tranny. No visible leaks on exhaust.

My last boat was a 5.8 PCM w/o EFI and was a bit easier to figure out. Do I need to trailer to a dealer so they can read the code or are there any troubleshooting tips?

Does this engine have a Throttle Position Sensor? My friend said probably not. If it does, can that be an issue?

Thanks

Jay

[M3Fan]

RE: GT 40 Acceleration Problem at Higher RPM

It does have a throttle position sensor. I'm curious as to what the problem is. You can download the troubleshooting guide for that engine on the Downloads page of this site IIRC.

[JayG80]

RE: GT 40 Acceleration Problem at Higher RPM

Thanks, I have been reading Sec 3E7 and will post a solution when I find it.

[SGY]

RE: GT 40 Acceleration Problem at Higher RPM

What about fuel pump and fuel filter?

[JayG80]

GT 40 Acceleration Problem at Higher RPM

It was the fuel pump.

I put a pressure gauge on the valve on top of the FCC and had 35 lbs at idle but it dropped to 20 lbs at full throttle.

New fuel pump and it is good as new.

Looked at the plugs again and they were a bit white or ashen.

Thanks for the help, it is nice to have this resource!

Jay