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03 Wakesetter vlx monsoon Sluggish\no power

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I’ve been having a similar issue as the post by tbullard concering loss of rpm on an 03 wakesetter vlx with the 335 monsoon. I had this post there but decided maybe I should start my own.

  I have had 0 problems from this boat and it has run flawlessly for many years and I bought it from the original owner in 2004.  The boat stays covered in a boat house.  A few weeks ago I unexpectedly had to run  it up the lake to a friends house on the lake.  I usually bring gas with me and haul it down to the pier vs. getting gas at the one marina\store on the lake.  I had no choice but to stop and get 10 gal on the lake in order to make it back.  The boat ran fine for the rest of that day.  Flash forward two weekends, and the boat cranked fine and idles fine but is extremely sluggish out of the hole with no top end power. I can disengage the transmission with the button and seems to rev to normal rpm range with no problem, so the problem is only under load .  It is  So bad I don’’t think I could pull a kid on a tube much less a skier\or wakeboarder out of the hole. It has been consistently that way since memorial day as I have slowly tried to eliminate simple possiblities before getting too drastic.

I’ve read about every relevant thread on here that I could find, so I started with the obvious.  

I have:

changed the fuel filter( very little change if any after)

Pulled the fuel pump and cleaned the screen on the low pressure side.

checked fuel pressure (42 on gauge )

New plugs, wires, icm .  (Cap and rotor were changed couple years ago, so I haven’t done that again YET!, they still look very clean as if just out of the box.)

Just bought a new coil today and was going to give that a try this weekend before I get into draining the fuel tank or trying water remover or whatever else I might try fuel related. Fuel would make the most sense considering the unusual stop at the marina, but these things always seem to happen when there’s something else involved to make you chase the wrong thing.

Is HEET with fuel injector cleaner worth trying? I have had no backfiring or missing or issue cranking ...... just simply sluggish with no power.

The only other odd thing since this started is that. the shift into forward has gotten extremely rough with hesitation going into gear at the first inch or so of moving the throttle forward. Once engaged, everything seems normal.  I checked all fluid levels and looked closely at fluid color and all seems normal.

Any suggestions are welcome!  Thanks in advance!  

Edited by HWY61
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26 minutes ago, tbullard said:

Have you tried reading the fault codes from the computer using the LED and Jumper method I linked to in my thread?

No I have not. I just checked that link out. I had been eyeing the code mate tool, but had not seen this method. I’ll give that a try if the new coil doesn’t help.

Hopefully I’ll get a code  that will reveal something to end this guessing game. Thanks. 

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Not sure why you would do plugs and wires without doing the cap and rotor.  Should be one of the first things you do -- and a "couple of years old" tells me it very well could be time for a change!

My 2004 had the same problems last year and a new cap/rotor solved it immediately.  Of course, my cap and rotor LOOKED awful but I still wouldn't discount yours being good.  These are a wear item and should be replaced as part of any tune-up.

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7 hours ago, Fffrank said:

Not sure why you would do plugs and wires without doing the cap and rotor.  Should be one of the first things you do -- and a "couple of years old" tells me it very well could be time for a change!

My 2004 had the same problems last year and a new cap/rotor solved it immediately.  Of course, my cap and rotor LOOKED awful but I still wouldn't discount yours being good.  These are a wear item and should be replaced as part of any tune-up.

I don’t disagree, but I probably haven’t put 20 hours on the boat in that two year period. And I didn’t change plug wires back then. I’ll probably go ahead and change cap and rotor just to get everything on the same schedule. 

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I have now replaced cap,rotor, icm, coil, plug wires and plugs.( all of which probably needed replacing anyway.) No noticeable change. I double checked firing order and wires etc.  all seems correct.

I also did the diy code reader with LED light successfully.  Got a 1 blink——2 blink code repeatedly.  So unless i’m misunderstanding, all seems normal there.

Bc of the marina gas issue, I decided to go ahead and siphon the tank today.  Put in fresh gas and another new fuel filter.  It is running much better, but still slow out of the hole and tops out around 3000 rpm.  Its running decent at best but just doesnt have that pep that it normally has.  Almost has a choked out sound at WOT. It runs the best at around 3/4 throttle.  

Should I just keep running it with some fuel treatment\injector cleaner and hope it works itself out,  bc the gas was at very least part of the problem or possibly the cause of a different one.?? 

Should I move on to injectors?

Are there any sensors that I should check that  won’t throw a code?  Fuel pressure regulator or anything else?

Also, what should the fuel pressure be at say 1/2 throttle under way?

Any suggestions welcome.  Thanks!



Edited by HWY61
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10 minutes ago, HWY61 said:

Also, what should the fuel pressure be at say 1/2 throttle under way?


Your fuel pressure regulator is referenced to manifold pressure.  Since there is vacuum at idle, the fuel pressure is lower than at WOT.  GM is trying to keep the same fuel pressure drop across the injectors at all throttle positions.



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After ruling out everything else, I decided to pull the injectors today.  About 3 of the 8 were almost fully clogged at the top screen. In an effort to try to get on the water for the weekend, I cleaned the top screens on all injectors with carb cleaner to the point where I could only see screen visible on all injectors and then got everything  put back together.  I swear to you the boat didn’t have this much power when I bought it in 05.  Its like a different boat.  I guess Cleaning those screens and all of the ignition updates I’ve done have awakened the beast.  I intend to pull the injectors at the end of the season and have them thorougly cleaned.  I hope this has resolved all my issues.  Thanks to those who gave me advice.  

  • Like 2
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Well, after running a little while this morning , I started having a brief miss\loss power for a split second and then it will correct.  Overall still running great.  This miss is intermittent .  I went back in and rigged up my diy led scan and seem to be getting a code 81.  From what I read, The actual scan tool is needed to get more info on an 81 code? However, from what I read it seems that injector voltage etc is sometimes associated with an 81.

Any suggestions on what I might check in light of just pulling the injectors. ?

As far as I know, I have all sensors replugged correctly, and I took great care to not damage or be to rough  with the fuel injector wires.   

Only other thing is the gasket when I took air intake off the top, did have  couple small damaged places where it seperated itself half -in-two top to bottom..... Leaving some on top  and some on bottom, but it seemed to be enough thickness remaining to reseal.  Should I have put a new gasket or gasket sealer?  It would make sense if there was a leak there it could be throwing things out of wack with a sensor.?

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schematic shows all injector wiring goes thru a connector. 

i'd pull that connector apart and have a good look for mis-shaped/mis-aligned/corrosion/etc.

after review, strike this, you have already done it: would not hurt to take a look at each injectors connector, too.

Edited by tvano
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I had same issue with my injectors. Read some of my older posts about them. I also had a failing fuel pump and had to setup a second low pressure fuel pump once i got the new high pressure. I custom plumbed an 8 micron filterjust before the fuel rail after i sent my injectors out for cleaning. 

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As of now she’s running perfectly. I guess it just needed a little runtime with cleaner injectors to work through whatever contaminants that were remaining. Ran for a few hours  late yesterday with no misses. Fingers crossed that I’m done messing with it for the summer.

My takeaway from all this is that dirty injectors can be a slow and somewhat unnoticeable process of decline  over a 10-15 year period even on a low hour boat. You don’t realize how much performance you’ve lost until you get it back. The thing takes off like a jet ski now!.  I’m scared to see what it will do when I have them professionally cleaned. 


  • Like 1
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  • 1 year later...

Its a standard gm injector but id pull all of them and send out for ultrasonic cleaning at a shop that specializes in that. Fuel injection connection in Atlanta I think is a place i sent mine to. They rebuild, clean, flow test. Put an 8 or smaller micron high pressure filter after the fuel pump so you can help prevent all the junk that will clog the injectors. I think the fuel pump sheds material.  

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