Fuel starvation under power

[Rick 1998 air nautique]

I have a 1998 Air Nautique (GT40). I have read most of the fuel post. The boat will run intermittently rough under power ( skier out of hole or 17 knots accelerating). Pull throttle back it is fine. Between me and a mechanic I have in order
Replaced fuel filter
added fuel stabilizer ( I always run ethanol free)
changed spark plugs
replaced fuel regulator (boat mechanic)
replaced high pressure fuel pump
inspected anti- siphon valve
pulled fuel pickup and checked screen

There is a fuel vent line check valve. I tried putting pressure from fuel tank line with almost no air coming out hull side. I then put pressure from outside overflow and had more air come through to disconnected fuel vent line. Not sure how check valve works or how to check it. Ideas?

Not sure how to load picture from phone URL?
I have not replaced relay for fuel pumps. Low pressure pump seems to work fine. Help?

[Chris Parsons]

Did you ever figure this out?

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[wakeboarder3780]

Have you ever drained the gas tank and put all new fresh gas in? Wondering if you have a bit of water in the tank?

[Rick 1998 air nautique]

No I have not solved the problem. Since I wrote this thread I have replaced the plug wires and Cap. I have also replaced the computer and a mechanic pulled and cleaned the fuel injectors. It is now at the Nautique dealer in Cleveland Tn. It will be a sad day if it was water in the tank but if it will run again as it use too I will be happy.

[COwake]

Hello, so I had a similar issue on my boat. Different engine however maybe my findings will help you. Boat would run fine until we were loaded down on ballast and surfing. Then it would be running along fine and just fall on its face and start surging. Finally it threw a misfire code on cylinder number 8. I tried replacing spark plugs, the coil pack, fuel filters, and the injector on cylinder 8. I hooked up my fuel pressure gauge and could see the fuel pressure fluttering at the same time the issue was occurring. So I replaced the fuel pump relay aswell. Didn’t get a chance to test it again before winterization however. Then when bringing the boat out of hibernation and trying to run it on the hose it would even stay idling. I could cycle the on switch a few times and it would only build enough fuel pressure to start for a few seconds. I got to digging around and found cracked hose on the first fuel filter housing between the tank and the fuel control cell. I believe that it was sucking air as both fuel pumps were down stream from the leaking connection. I fixed that and haven’t had an issue in about 15-20 hours of operation. I would look for a leak in your fuel system to see if is sucking air. Good Luck.

[gun-driver]

Could be this they have been known to crack/deteriorate and draw in air.
https://nautiqueparts.com/internal-fuel-hose-for-fcc/
Or
There is a screen in the bottom of the low pressure pump, that could be partially clogged not allowing enough fuel through during higher acceleration.

Best way to diagnose fuel system issues is with a pressure gauge.

[Rick 1998 air nautique]

Co Wake
i have hade the boat at a different NAUTIQUE dealer for almost 4 weeks. I inspected that hose but did not replace ( should have): since this text I have replaced plugs and cap. I have replaced computer and had injectors cleaned and inspected. I did run the motor with fuel pressure gauge and it ran steady during rough/loss of power. The new shop has started over and the last thing they replaced was coil. They are ordering a new diagnostic computer. Fuel has been checked multiple times but never dumped. I have put a lot of fuel in this boat since last year when it started acting up. I am working with shop on draining it but I have to drive two ours and give them something to catch gas and discard myself?

I have just kind of given up and put in pros hands!

Frustrated owner of boat he loves