GT-40 Losing Power, need help

[braibert]

I have a 1997 Ski Nautique with the GT-40 engine that is having a major loss of power. I have scanned the other posts on this but went ahead and started a new thread.

When picking up a skier you keep pushing the throttle down and you do not get near the expected throttle power. The boat can not run a good time at 34 mph and 36 mph pass running with perfect pass on or off. When the skier pulls, the boat bogs down. Sometimes there is a slight surge like the boat wants to run stronger. At idle the boat runs a little rough but not too noticeable.
The wide open throttle(WOT) is now only going 36 mph and about 3900 RPM. The boat usually is about 43 mph and 4400 RPM at WOT.

Recent History(ski days are 2-3 days apart):
- Full gas tank of 91 Octane, skied two days no problem
- Replace Ignition solenoid at the ECM (it has be flaky for years), skied one day no problem.
- Loss of power begins on the next ski day, two days later.
- Replace fuel filter, clean high volume fuel filter screen, replace spark plugs
- Ski two days later, a little better but still much loss of power
- Replace cap and rotor, test boat, still the power is not available and WOT is only 36 mph without a skier in tow

Other:
- Check engine light does not come on
- Engine does not sound like it is not miss-firing
- Feels like the boat is going into limp mode?

Thanks for the input,
Bob

[nms1991]

Braibert you need to check your fuel pressure to see if you have the right fuel pressure at idle and at high speed. When you changed the fuel filter did you check your hose inside of the fuel control canister. If the boat is a early production 97 it could need a update for that hose, the proper hose is black and not transparent. Your local nautique dealer should be able to get the part from PCM.

[braibert]

This is exactly what it was. The hose was black but had a small bend in it which over time caused a small pin hole. The pressure would not hold at idle and at speed.

Neil at M2O Marine did a great job.

Thanks.