Boat engine issues

[stuartsx5]

I purchased a 2007 Nitro with a 150 Mercury 150 EFI. Boat ran great for the test drive but when I put on the lake the next time after about 6 miles it gave me some problems. At WOT it will start bogging down them it starts cutting out\miss firing. Changes the fuel filter but kind if at a loss on what to look at next, fire or fuel. It has 120 compression on all cylinders. Looks like 3 coil packs are new and 3 are original.  I shot a video of it yesterday but can't upload here so I uploaded to YouTube. This is the link

Thanks in advance for any advice

 

[fishinwrench]

Do you have a Voltmeter on the helm ? 

If so what does it indicate when the engine begins to fall on its face?    Is the tach working (not jumping around and acting silly) ?  

My first impression is that either a voltage regulator has failed, High speed side of the stator is failing, Or the fuel pump driver in the ECM is going south (check the big harness plug that connects the ECM, make sure it is clean and tight).   

Does the motor actually die.....or just cut back to a lower RPM?

[stuartsx5]

Thanks for the reply.  I was so focused on it being fuel at the time I never thought to check those things.  I will put it on the water again and look at those things.  I will check the plug in the ECM.  It doesn't die, it will bog down like it is starving for fuel then start doing what it shows in the video, cutting in and out.  As long as I keep it down around 3,000 it runs fine.  It has enough power to push it back up on the trailer and it purrs like a kitten at idle even after it acts up.  Thanks again for the help, I will post what I find out on those other things. It may be a next week sometime before I can get it on the water.

[stuartsx5]

Quick question, is the voltage regulator in the alternator? Probably a silly question but I can't find it.

[fishinwrench]

3 hours ago, stuartsx5 said:

Quick question, is the voltage regulator in the alternator? Probably a silly question but I can't find it.

No, the voltage regulator (there's actually 2 of them) is on the back exhaust plate of the powerhead.  Underneath the plate that the ignition coils and tilt/trim relays are mounted to.   

This is assuming that your's is standard 150 EFI.   Will need the serial number to confirm if it is equipped with a belt driven alternator. 

Just follow the yellow wires coming from the stator (under the flywheel) .

[stuartsx5]

Thanks for the info. I added a pic of the model and serial numbers. 

[fishinwrench]

Oh Great 🙄 

Belt driven alternator and CDI coils.  

You're gonna have to visit a Mercury dealer and have them do computer diagnostics on it.     I'm sure it stored a code. 

Hope like hell that it isn't a bad TPS because they are No Longer Available.

[stuartsx5]

OK. 😕 that doesn't sound good. Just to clarify, with the alternator, do I still have the stator? I can see the alternator but no stator.

[fishinwrench]

No, no stator, and no trigger (timer base). 

Instead you have an alternator & crankshaft position sensor that control ignition and injector timing. And a TPS that controls injector pulse width.....All through the ECM. 

Beings as how yours comes up on plane and runs for a short time at elevated throttle settings.... I'm going to say that the TPS and CPS are likely fine, and that there is a bad wire or bad connection somewhere in the harness....or one of the harness plugs, causing an interruption there.   The troubleshooting software is NOT going to tell them where the fault is, but nevertheless the proper way to fix the issue requires access to the diagnostic program.  

[stuartsx5]

Thank you. I will head down this road and see where I end up. I will post back here to follow up.