I need help with 2017 G23 H6 not wanting to run under load/throttle

[zmnypit]

Figured Id make a new thread as my other one was mainly tied to my alternator problem. So about a month ago I pulled my g23 out of the basement, put the raw water plugs in the manifolds, charged the batteries and thought I was ready for the lake. 3 weeks ago we take it to the marina it stays out put it in the water and all seemed well until we cleared the no wake zone. The boat would run up to 2500 rpm/9-10mph no problem. However once it was under load it would start popping and struggle to run until you brought the throttle back down to below 2500rpm. I thought ok, water in the gas and its fine. Took the filter off drained it 4-5 times, drained the fcc twice and tried again with same result. We spent a good 2-3hr on the water just trying to burn the fuel so I could refill but the alternator had other plans. Batteries drained down to 6.6v per the screen and somehow managed to make it back to the marina. Alternator and fusible link/cable and battery was replaced so that problem is solved. Fast forward to present time and I still cannot get this boat to run correctly driveway on the hose.

Symptoms are: Its hard to start meaning it takes 2-3 presses of the start button before it will run. With any normal throttle speed it will not rev over 2500rpm. Once you cross that point you get popping sounds and it wants to die until you throttle off. However if you ease into the throttle slowly it will rev up just fine. (cant say what it does under load this way).

So far I've done the following:
- Syphoned 53gal of dark colored gas out of the tank, replaced with 15gal of fresh 87 (gas gauge shows 0% maybe unrelated)
- New spark plugs
- New fuel/water separator
- New HP fuel pump
- New FCC filter Kit
- New Alternator
- New 125a fusible link
- Pulled the separator off after running for 30min and no visible signs of water in the bottom of a clear glass

I've called two dealers in the state that work on Nautique and all are 6-8 weeks out on repairs. Thus the reason I'd like to sort this out myself so we can at least get some use out of it.

See below for a video of issues:

[g_force]

I know that you've received lots of guesses, but let me add mine.

If this were a car, I would say that the rough running, blown fusable link, and gas gauge reading 0% despite a full tank could all have the same root cause - a bad ground. Appreciating that you've done some wire tracing in trying to find the cause of the blown fusable link, if you didn't, maybe clean and inspect your major grounds and check the cables to ensure the cable ends are all securely attached, the sheathing is intact and the wires not corroded (esp. under the sheathing).

Good luck.

[zmnypit]

I know that you've received lots of guesses, but let me add mine.

If this were a car, I would say that the rough running, blown fusable link, and gas gauge reading 0% despite a full tank could all have the same root cause - a bad ground. Appreciating that you've done some wire tracing in trying to find the cause of the blown fusable link, if you didn't, maybe clean and inspect your major grounds and check the cables to ensure the cable ends are all securely attached, the sheathing is intact and the wires not corroded (esp. under the sheathing).

Good luck.

Thanks for the reply. I actually made an appointment with a dealer further away. I'm taking it Tomorrow and let them deal with with it. All I'm doing is wasting time guessing what could be wrong. I'll have them scan it and see what's going on.

[stereoman405]

Have you tested batteries out? I've had electrical gremlins that looked like bad alt / grounds be a dead headed cell in a battery. Spent HOUR chasing my tale. You would see a behavior change if you ran blower / stereo, pretty much anything with a current draw.

I've also had the throttle control box cause similar issue, especially the hard start. I have had one go bad on 2016 and 2017 G23 and another 2017 I just bought appears to have one failing. The tell tale sig then are goin is if the neutral button doesn't work. Every one of mine that has had that act up ends u failing within a season or two. Usually covered under warranty if your boat has under 500 hours on it.

[zmnypit]

Have you tested batteries out? I've had electrical gremlins that looked like bad alt / grounds be a dead headed cell in a battery. Spent HOUR chasing my tale. You would see a behavior change if you ran blower / stereo, pretty much anything with a current draw.

I've also had the throttle control box cause similar issue, especially the hard start. I have had one go bad on 2016 and 2017 G23 and another 2017 I just bought appears to have one failing. The tell tale sig then are goin is if the neutral button doesn't work. Every one of mine that has had that act up ends u failing within a season or two. Usually covered under warranty if your boat has under 500 hours on it.

Replaced the #2 battery as it was dead. No change in the popping with the radio, blower and lights on.

The neutral button still works and it has 120hr now. 2hr which are idling in the driveway on the hose. Dropped it off this morning with the dealership so will reply back once I'm told the issue.

[g_force]

Zmnypit, any report on what the problem was?

[zmnypit]

Zmnypit, any report on what the problem was?

Called the dealership this morning but they haven't called me back. I was originally told 2-3 weeks and yesterday was a week. Hopefully hear something before next weekend.

[zmnypit]

Called the dealership yesterday as its been two weeks and the wife if getting antsy before a long weekend. He said the mechanic had the work order on his desk Tuesday but doesn't have any info as of yet. Looking like may be a bit before I know anything or have it back.

[zmnypit]

7/23 update: Still no update and summer is slipping away and Ive all but written off this year. I've gotten conflicting stories so every thing may not be accurate. 7/2 I called for an update and was told they suspect the TPS sensor to be bad and would need to order it. Being a GM part I offered to go buy one and bring it down Saturday morning but was told there's no mechanics working on Saturdays and it would be in Monday. Called that following Tues as I never received a call back with an update. I was told the TPS sensor was in but hasn't been installed yet. Once again no call/update so I called again Friday 7/9 and was told diacom software showed slight misfire on cylinder 1 so the mechanic was checking the plug/wire and broke the plug wire off then the actual plug itself and the manifold had to come off to replace the plug wire. Upon taking the manifold off a blown manifold gasket was found (Which I find hard to believe as there was no indication of a blown gasket neither on or off the water) none the less the new gasket was to be in 7/12 and it would be put together and lake tested. Once again no call from the service dept and I called every Monday, Wed & Fri from then until now only to be told "its together just needs lake tested". Come to find out that was a lie. I have to get the actual manager of the location involved.

He called me today and said they got the new plugs, wire, tps & exhaust manifold gasket together yesterday and lake tested today and same issues still there. You can ease the throttle over time to wide open and it will sustain but if you hammer down from idle or slow speed it spits, sputters, pops and falls on its face. They took it to their other marina and had their mechanics run it for 30min with diacom and there's no codes, errors or anything out of the ordinary so they too are at a loss.

The manager said if I can find anything to test then send it to him so here I am. Between an angry wife, a ruined summer and empty promises I still have a non operable boat and not sure what to do.

[GMLIII]

Can dealer give you a loaner boat till yours is repaired ?

[scottb7]

I am not sure why replacing a plug wire would require removing exhaust manifold. Anyway, I wonder if you got a failing fuel pump, that maybe only low pressure pump putting out enough fuel at idle....but maybe high pressure pump not working or something like that.

Here is a quote from another thread "Check fuel pressure. Your high pressure pump might be having issues as well. The low pressure supplies the volume and the high pressure supplies the appropriate pressure to the injectors. Also, have you replaced the fuel filter recently?"

[zmnypit]

I am not sure why replacing a plug wire would require removing exhaust manifold. Anyway, I wonder if you got a failing fuel pump, that maybe only low pressure pump putting out enough fuel at idle....but maybe high pressure pump not working or something like that.

Here is a quote from another thread "Check fuel pressure. Your high pressure pump might be having issues as well. The low pressure supplies the volume and the high pressure supplies the appropriate pressure to the injectors. Also, have you replaced the fuel filter recently?"

Because the wire runs up the motor then to the coil pack behind the exhaust manifold. That's the only way to swap it out. High pressure pump has been replaced as well as both filters. I'm sure they checked the rail pressure but going to ask Monday.

[zmnypit]

Can dealer give you a loaner boat till yours is repaired ?

If they had inventory maybe. Pretty much bare at all thier showrooms

[zmnypit]

Quick update. So I'm told there's actually 3 pumps on the H6. There's a mechanical high pressure pump under the intake manifold that should be around 3000psi at higher RPMs. They checked it this morning and only getting 500psi. New one is ordered so will update once its replaced and I'm told if it worked or not.

[zmnypit]

8/5/21 update. High pressure mechanical pump replaced, boat reassembled and ran on the hose with same issues. So now the ECU, throttle control lever, tps, both high pressure pumps, filters, plugs, manifold gaskets and something else I'm forgetting has been tested or replaced at the dealer with no change. They are working with PCM to check wiring now.