2000 Super Sport with GT40 Check Engine Light

[Need2SkiT]

Yesterday I was out on the lake with my 2000 Super Sport with the GT40 motor. While cruising it would feel like the boat would just die and then surge again. After a little while the check engine light came on. The boat smelled like it was running rich. We made it back to the dock and I've replaced the spark plugs but all of the plugs seemed fine that I replaced. I've read where some people say it's the O2 sensor and I ordered one but then someone on the Nautique facebook page said the GT40 didn't have an O2 sensor. What should I be looking for? Help, we have company coming next weekend and need the boat back up and running by then. Thanks in advance!

[NautiqueJeff]

Very simple. Only two things can activate the check engine light in a GT-40. One is an overheat condition being sensed, and one is a low oil pressure condition being sensed. If you really are experiencing either of those conditions, you need to figure out why. Sometimes the switches that control the limp mode fail though, and activate limp mode even though there is no real issue. This would cause your gauges to read normal readings, but the switches for the SLOW system are signaling a problem, even though there is none. These switches are SEPARATE from the sensors for the gauges.

My bet is that the oil pressure switch has failed. You can disconnect the wire from that switch, and that should allow you to run the boat normally until you can get a new switch. It may also be the water temperature switch, and same deal with that, just disconnect the wire until you can get a new one and the boat will run fine.

Here's the oil pressure switch:
https://www.nautiqueparts.com/produc...nd-gm-to-2006/

Here's the water temperature switch:
https://www.nautiqueparts.com/produc...-mpi-r020014a/

We're talking about the SLOW system here. See diagram below.

These are the ONLY things that can trigger limp mode. Nothing else can do it.

[Need2SkiT]

And everything was fine. Temp was normal, oil pressure was normal. It feels like it has a foul spark plug and is running rich. It can't be either temp or oil pressure.

[Peter6000]

Yesterday I was out on the lake with my 2000 Super Sport with the GT40 motor. While cruising it would feel like the boat would just die and then surge again. After a little while the check engine light came on. The boat smelled like it was running rich. We made it back to the dock and I've replaced the spark plugs but all of the plugs seemed fine that I replaced. I've read where some people say it's the O2 sensor and I ordered one but then someone on the Nautique facebook page said the GT40 didn't have an O2 sensor. What should I be looking for? Help, we have company coming next weekend and need the boat back up and running by then. Thanks in advance!

No O2 sensor, the red light only comes on for overheating cooling water or low oil pressure.
To test you can disconnect both sensors.
The are both switches.
Also check your oil pressure and temp gauges. If the show normal one of the sensors is bad.
Oil pressure I kind of low behind the bigger fuel pump.
Temp is on the top front left.
Get the pro boss service manual for exact location it's under manuals in this forum.

Sent from my SAMSUNG-SM-G870A using Tapatalk

[NautiqueJeff]

Those are the only things that will make the light come on. Nothing else triggers it.

You have a temp or oil pressure switch that has failed. The sensors (not the switches) feed the gauges, so if everything looks good on the gauges and you're still getting a light, one of the switches has failed.

[Need2SkiT]

Would either of those cause the boat to just completely lose power and then kick right back in again? Only losing power for a split second and then power up again.How about making it run rich?

[NautiqueJeff]

Yes. That's limp mode. It happens when the light comes on.

[Need2SkiT]

Thanks Jeff. I might try to run it over to the lake on Wednesday and see if I can locate either of those sensors and disconnect them and see if that works. I appreciate the quick feedback. So does the GT40 not have an o2 sensor?

[NautiqueJeff]

Which lake? If you're going to be close to my place on Lake Norman, I can help you.

I don't believe the GT-40 has an O2 sensor.

[Need2SkiT]

I’m probably only going to have time to run to Lake James on Wednesday. Which part of Norman are you on? I don’t think I can cut out enough time to run over there unfortunately. Thanks a bunch for the offer though. I really appreciate it!


Sent from my iPhone using PLT Nautique

[gcam4]

Gt40 doesn't have a lambda sensor as Jeff mentioned. As others have mentioned it is likely one of your sensors for the dummy has failed. I can also help you if you need it, I'm in Davidson.

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[gun-driver]

I wouldn’t order anything from a place that sold you an O2 sensor for a GT-40 Or take any of their advise.

[Need2SkiT]

I’m assuming this is what I’m looking for right? There’s a tee behind this and a wire that has a nut holding it off a little round cylinder thing tee’d off this.

[Peter6000]

I’m assuming this is what I’m looking for right? There’s a tee behind this and a wire that has a nut holding it off a little round cylinder thing tee’d off this.

That's the oil pressure sensor it controls the gauge, the should be a smaller one behind it. Don't see it in the picture.

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[NautiqueJeff]

That's the sensor. You need to disconnect the wire from the switch (wire that has a nut holding it off a little round cylinder thing tee’d off this).