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Engine sputtering over 2500 rpm while towing a tuber.


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I have a 2004 wakesetter vlx. After about a half hour on the water the engine begins to sputter if I go over 2500 rpm while towing a tuber. Runs fine if I stay under 2500, and runs fine over 2500 if there is nothing in tow. I've changed fuel filter, full tune up with new plugs, cables, distributer cap. Still can't figure this one out. Acts as if the fuel it getting cut off and starts to sputter Bradley.

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1 hour ago, Shipman said:

I have a 2004 wakesetter vlx. After about a half hour on the water the engine begins to sputter if I go over 2500 rpm while towing a tuber. Runs fine if I stay under 2500, and runs fine over 2500 if there is nothing in tow. I've changed fuel filter, full tune up with new plugs, cables, distributer cap. Still can't figure this one out. Acts as if the fuel it getting cut off and starts to sputter Bradley.

You didn't say which engine you have.  It might be a good thing to test your fuel pressure with key on, at idle, and at wide open throttle.  They should all be the same.  If you have a Monsoon, the plenum cover may interfere with your ability to get a regular gauge on the test port.  You could adapt a tire chuck to the job or remove the plenum cover and cut the flange above the port and reinstall it.

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5 minutes ago, Shipman said:

It is the indmar engine.

Hmmmm.  More specific, please, or post a photo.

Does it look something like this?

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Or maybe like this (with the plastic cover removed)?

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Or neither of those?

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3 minutes ago, Shipman said:

The second one

That is the LCR engine.  The good news is that you can just thread your fuel pressure gauge on the schrader valve really easily.  It is a 3 Bar fuel system, so you should have 3 Bar * 14.7 PSI/Bar = 44.1 PSI on the fuel rail.  Realistically, it will generally be about 42 PSI or so.  Check it at key on, at idle, and at wide open throttle. 

Pressure too high probably means bad regulator.

Pressure too low probably means a blockage or failing pump.

Pressure just right means that something else is wrong.

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Not really a mechanic but I will try to take a look. Just really frustrating. Second year dealing with this same issue. 

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4 minutes ago, Shipman said:

Not really a mechanic but I will try to take a look. Just really frustrating. Second year dealing with this same issue. 

You should have joined sooner!

A fuel gauge is fairly cheap and easy to use.  It is usually the first instrument you would use to diagnose a misfire on your engine.  An auto parts store may loan or rent one to you if you don't care to own one.  A neighbor might have one.  Try the guy down the street with the older pickup that always seems to have stuff in the back....

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When you have a tuber in tow are you maneuvering aggressively?  Wondering if the sputtering is due to intermittent fuel pressure problems due to sloshing in the tank or some such?  A tube on plane behind a boat is not much load.  Hard to believe that the drag of a tube is the difference in load that trigger this.

On a similar note I worry about oil pickup when pulling teenage and older male riders.  Never have seen a production dry sump ski boat so figure it just me thinking that.

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Not too aggressive..once it starts sputtering, it doesn't stop over 2500 rpm. If I throttle below 2500 it will run but that is not a fun tubing speed. Again only under load towing a tube. It's really wierd.

 

Lance

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It is also possible that your fuel hoses are breaking down on the insides, especially if you use alcohol fuel.  I have had a hose that dislodged chunks of rubber inside and clogged it.  The most interesting thing was that I was testing the hose by blowing backwards toward the tank, and it flowed very easily.  It wasn't until I remove the tank end and blew in the forward direction that I discovered the restricted flow.

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34 minutes ago, Shipman said:

I believe that was done as well with the tube up.

I ask only because many years ago I helped a friend with an issue and we ended up removing and either replacing or testing EVERYTHING in the electrical system...turns out, he bought the cap but not the rotor, as it looked brand new when he took off the cap.  Well, the problem was the connection under the rotor; it was corroded as can be but looked to be perfect. 

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Update, problem still persists. Once the sputtering starts (after about 39 minutes) it seems to be rpm dependent. If I stay below 2500 it runs fine. If I go over, it bogs and sputters like it's going to stall. Is there some type of sensor that could be involved or does this seems like a fuel delivery issue.

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1 hour ago, Shipman said:

Update, problem still persists. Once the sputtering starts (after about 39 minutes) it seems to be rpm dependent. If I stay below 2500 it runs fine. If I go over, it bogs and sputters like it's going to stall. Is there some type of sensor that could be involved or does this seems like a fuel delivery issue.

...and the fuel pressure while it happens is...?

  • Like 3
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@Shipman - did you have the tune up done or did you do it?  Sounds like another party did it, what is their troubleshooting diagnosis?  As per previous comment, a fuel pressure test will help diagnose the root cause. Also, along with fuel line blockage, a corroded anti siphon valve has similar symptoms.

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Rotor was replaced with tune up in spring. Still trying to locate a fuel pressure gauge.

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  • 2 weeks later...

Had boat out again today. Full tank of rec gas. Same problem. Starting to think it is a sensor or ignition issue. Definitely rpm.dependent after boat running for about 49 minutes. 

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Update and question. I was looking at the trans cooler connections in efforts to see if there were any obstructions. While doing so I noticed a wire connection not plugged in on the alternator. Not sure what it is for but I plugged it back in. Could this be my issue?

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5 hours ago, Shipman said:

Update and question. I was looking at the trans cooler connections in efforts to see if there were any obstructions. While doing so I noticed a wire connection not plugged in on the alternator. Not sure what it is for but I plugged it back in. Could this be my issue?

Have you checked the fuel pressure as @JustGary suggested?  If not, check the fuel pressure next.   If you have low fuel pressure then you know you need a fuel pump or you have a clogged up fuel system. If fuel pressure is fine then we can work on solving the ignition problem.  

Edited by Bozboat
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1 hour ago, Bozboat said:

Have you checked the fuel pressure as @JustGary suggested?  If not, check the fuel pressure next.   If you have low fuel pressure then you know you need a fuel pump or you have a clogged up fuel system. If fuel pressure is fine then we can work on solving the ignition problem.  

That's not going to happen, Boz.  Two years with this problem and no action....  Nothing like continuous hypothecation to solve problems.

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