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CameronVLX

Misfire, running rough, skipping at wakeboard speeds, surf apeeds, under load

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CameronVLX

So after reading a lot of post, lots of searching this forum, lots of my own diagnosis.  I found the problem.

 

My 2003 malibu VLX Monson 335, has had a random skip at most surf or wake speeds only when weighted with balast or with wedge down.  So basically under heavy load.  I am an automotive mechanic and would describe it as a cylinder dropping.  But it was random and would last anywhere from 2 seconds to 7 seconds, but would get worse and then go away.  Sometimes come back and be present for some time.  Usually would go away with a little time at rest.  (Key off)

I tried all the basic stuff, cap, rotor, wires, plugs, fuel (drained tank), and fuel filter.  Even got duped by a bad plug wire (bad brand new out of the box)

So after some sea trials I realized it could only be in the fuel system.  I pulled the injectors and found a lot of trash in the fuel rail side of the injector.  A couple of injectors were full to the top of the cavity.  Luckily there is a screen in the intake side of the injector.  In the process of cleaning them now.  I will follow up on the repair in the next week.  Waiting on an intake gasket to finish the repair.

 

Edited by CameronVLX

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mikeo

This has been a common fault reported recently, I wonder if there is something that is driving higher levels of contaminants in fuel... Check out this thread from last year when another member sent his injectors out to be cleaned:

 

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CameronVLX

I want to blame the corn liquor in our fuel, but the previous owner may be the real culprit.  I haven't owned the boat very long.

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ChainSetter

I had a similar issue that always throws service required if I drive the boat over 40.  When I start it, it starts then almost dies twice, then runs perfectly as long as I don't go over 40 mph.  I've changed fuel pump, filter, had injectors cleaned, plugs, wires, and distributor cap.  I finally hoped the issue would be gone but it's not.  I've basically given up.  I always get a cylinder 1 misfire error

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MadMan
9 hours ago, ChainSetter said:

  I always get a cylinder 1 misfire error

This sounds more like an ignition/electrical issue more than fuel related.

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MichLivin

I have the same misfire issue, i have under a 100 hours on the boat and my gas tank was pretty empty over the winter so I could fresh gas in summer...  Hopefully its a small fix...

What the are the causes of misfire?  It happened when I loaded up the ballast tank and tried to run, last time out on the lake had no issues...

Does it sound like a fuel filter?

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CameronVLX

Well I have had the boat on the water since the injector cleaning.  Boat runs 90% better.  It's amazing how much little throttle it now takes to get on plane and cruise.  I still have an exhaust leak, and what sounds like spark knock during a hole shot.  I am going to try and isolate the exhaust leak and go from there.

Michlivin,

It could just be stale gas in your situation, or water in fuel.  Do you use stabil regularly?  These new fuels are terrible for boats and don't last when stored for long periods of time.

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MichLivin
On May 10, 2016 at 8:14 PM, CameronVLX said:

Well I have had the boat on the water since the injector cleaning.  Boat runs 90% better.  It's amazing how much little throttle it now takes to get on plane and cruise.  I still have an exhaust leak, and what sounds like spark knock during a hole shot.  I am going to try and isolate the exhaust leak and go from there.

Michlivin,

It could just be stale gas in your situation, or water in fuel.  Do you use stabil regularly?  These new fuels are terrible for boats and don't last when stored for long periods of time.

Cameron, I will try Stabil, I know 75% of my gas is fresh, having only a quarter tank through winter could have affected it.  As you said you never know...  For now I did also get a set of plugs, after 5 years of marine life I think I probably need a set

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CameronVLX

I know this topic is a little old, but I thought I would give an update.  I previously stated that the boat ran 90% better after cleaning the injectors and I thought I had an exhaust leak.  My exhaust leak turned out to be a backfire in the intake.  The clogged injectors did a number on my engine.  I decided to do a compression test after I lost a lot of power out on the lake.  The results were not good, 0 compression on cylinder 1.  I removed the head and found a burned intake valve on cylinder 1.  I have since repaired the valve and replaced all 8 injectors.  The boat now runs perfect.  I thought I would post this because some others out there with similar symptoms may be able to catch this soon enough to prevent major repairs.  I am assuming that prolonged running of the engine with clogged injectors caused a lean condition especially in cylinder 1 (very clogged injector) the excessive heat due to a lean burn caused the valve to stretch and no longer seat in the head.  I am an automotive mechanic so I saved some money on the repair (free labor) but it still cost me around $500 for parts including the new injectors.

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