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2008 Monsoon running rough


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Hopefully someone can steer me in the right direction before I have to haul to a mechanic. Sorry in advance for the long winded post.

Boat is 2008 LSV with the Monsoon 350 with about 460 hours which has run flawlessly until now. Putting the boat in for the first time on Memorial weekend. Friday afternoon boat starts right up and we do a checkout ride to make sure we don't have any water leaks or other gremlins and are out maybe 15 minutes without any problems. We are in no rush Saturday with all the crowds so we wait until late in the afternoon and put in for a cruise. Within 5-10 minutes the boat starts hesitating and surging and are able to finally make it back to the ramp and get the boat out. My wife is convinced it is 10 gallons of bad gas I bought in town instead of at the marina. I put in a bottle of HEET and changed the spark plugs since they were original. On Sunday we are doing electric work at the house so decide to try the boat again late afternoon and this time it will start for a few seconds and then shuts off.

I was able to get a fuel pressure gauge and it was showing 65-70 psi at key up and then took a sample of fuel from the gauge and it looked and smelled fine. Removed the plenum and distributor cap. This is the original cap was super corroded and surprised it ever cranked.

Replaced cap and rotor with marine units and tried to start yesterday morning. It starts but is hesitating/surging and will die after a few seconds. Borrowed a fuel gauge that afternoon but found it is really hard to access the schrader  valve with the plenum in place so I decide to just start it. Boat is running smooth on the trailer for about a minute so we launch and tool around for about an hour starting and stopping several times and varying the RPM's. It did not miss a beat.

Load up today with neighbor's kids and boat starts hesitating and surging less than a minute after launch. We were able to get back on trailer and then decided to have a cold one and wash the boat.

I'm not a mechanic by any stretch of the imagination and really don't know where to start but am willing to throw a few parts at it because the closets shops are at least an hour away and I honestly would not know which one to take it to.

Searching here seems like I should go ahead and replace the ICM (assuming I can get one at AutoZone) and not about the IAC and TPS. Not sure where the last two are even located.

Any suggestions are greatly appreciated.

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formulaben
59 minutes ago, BearCreekBum said:

...and changed the spark plugs since they were original.

...

This is the original cap was super corroded and surprised it ever cranked.

OK, I'm going to assume that this thing has never had any preventive maintenance.  Here is what I would replace before trying to troubleshoot any other parts:

  • Spark plugs (you already did)
  • Cap & rotor (you already did)
  • Spark plug wires (change them one at time!)
  • Coil (unless that model has coil packs)
  • Fuel filter
  • Air filter (clean only if it is a K&N style)

Change these and then run it on a fake-a-lake and report back.

 

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1 hour ago, formulaben said:

OK, I'm going to assume that this thing has never had any preventive maintenance.  Here is what I would replace before trying to troubleshoot any other parts:

  • Spark plugs (you already did)
  • Cap & rotor (you already did)
  • Spark plug wires (change them one at time!)
  • Coil (unless that model has coil packs)
  • Fuel filter
  • Air filter (clean only if it is a K&N style)

Change these and then run it on a fake-a-lake and report back.

 

I did clean the air filter. 

Does anyone know where the fuel filter is located? I assume it is in the tank with the fuel pump.

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  • 2 weeks later...
On 6/7/2020 at 9:39 PM, formulaben said:

OK, I'm going to assume that this thing has never had any preventive maintenance.  Here is what I would replace before trying to troubleshoot any other parts:

  • Spark plugs (you already did)
  • Cap & rotor (you already did)
  • Spark plug wires (change them one at time!)
  • Coil (unless that model has coil packs)
  • Fuel filter
  • Air filter (clean only if it is a K&N style)

Change these and then run it on a fake-a-lake and report back.

 

@formulaben

Finally got the wires and fuel filter changed but no improvements. Thought I had the coil locally but did not pan out.

We have 54 psi fuel pressure at key up and it stays between 54-60 psi for the short time it is running. It basically will run for 30 seconds one time and 3 seconds the next time. I’m afraid I’ll do more damage if I keep starting it.

Any suggestions are greatly appreciated but I guess I’m going to roll the dice and take it somewhere. 

Time to turn in my man card. 

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IDK if that boat still gad an ICM but it'd be worth swapping if it does. They're not all that expensive and can create all sorts of wacky problems. Coil also worth checking even if you have a buddy you have to borrow one from to test. 

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Yes changed the fuel filter on bottom of the pump.

I think the more I touch it the worse it gets. 

Last weekend the fuel pressure would go to 54 on key up and stay above 40 for hours. 

I just went to remove fuel pressure gauge and noticed it was on zero after only couple hours. First key up it goes to 54 and then to zero after 5 seconds.  Next key up it goes to 54 and when I turn key off immediately starts dropping. 

Time to work on the brakes so I ca drag to someone. 

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2 minutes ago, UWSkier said:

IDK if that boat still gad an ICM but it'd be worth swapping if it does. They're not all that expensive and can create all sorts of wacky problems. Coil also worth checking even if you have a buddy you have to borrow one from to test. 

From what I can tell the ICM and coil are mounted on one bracket. I went to O’Reilly and tried to find an ICM but the one they had was $100 and while it had the same pin layout but the guy had no idea if it would work. I would rather spend $175 for the Indmar to be safe. 

Ill let you guys know if we ever get it running. 

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@UWSkier @formulaben

Wanted to thank you guys for the suggestions. Saturday was a Murphy’s law end to a busy week at work and it beat me up. 

A day away and couple Weller 12 pours and I can’t stand not being able to figure this out. 

I bought a new ICM but didn’t have time to mess with it. Just for fun today I checked the resistance between the pins of the old ICM and the new ICM although I have no idea what I am measuring. On the new ICM, I measured a consistent 330 kohms between pin 1 and pins 2,3&4. On the old ICM the same measurements ranged from 230 kohm to 800 kohm.

If I can’t find a replacement assembly by the weekend I am going to change out the ICM and see what happens.

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Dont want to hijack this thread. But, similar testing for me. My '02 rough idle. Pressure at key up is 43. Pressure at idle is 42.5 ha. Think that is an issue? Wondering if I need a regulator to bring that sucker down.

Thanks so much in advance,

Steve B.

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4 hours ago, Steve B. said:

Dont want to hijack this thread. But, similar testing for me. My '02 rough idle. Pressure at key up is 43. Pressure at idle is 42.5 ha. Think that is an issue? Wondering if I need a regulator to bring that sucker down.

Thanks so much in advance,

Steve B.

You should be good.  Clean the throttle body. 

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I guess it was wishful thinking on my part. 

Replaced coil and ICM but no change. Boat will crank rough idle for few seconds and then quit. It doesn’t run long enough to do any diagnostics.

 I’m going to pull the cap and rotor tomorrow just to make sure I didn’t mess something up during installation. 

Any Hail Mary suggestions?

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  • 2 weeks later...

Finally some good news. Picked up the boat Saturday.

Turns out it was the ECM and that was the fix. Hope I'm good for another 12 years.

Appreciate all the suggestions.

  • Like 2
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