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Interesting problem. Fuel or ????


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Ruined another day on the water with yet another problem on my previously trustworthy sunsetter. 98 Vlx with 525 hours. 325 monsoon engine.

The boat was running fine until it the engine suddenly started hesitating and stalling above 2800 rpms. I know what you are thinking. Clogged fuel filters or screen in the pump. Changed them 12 engine hours ago and cleaned the screen as well. I also never buy gas at the marinas. What is interesting is that after this happens and the boat starts surging and backfiring I put the engine in neutral and the rpms only drop to 2100 before finally settling down to 800 after a minute or two. What would cause this?

By the way, the other interesting thing that happened this week is a broken alternator bracket. Replaced the alternator at the beginning of the summer with the nice 110 amp one from DB electrical. Unfortunately, the new one is much heavier than the original and the bracket can not support it. Of course the all happened on our one week summer boating vacation in northern MT.

Thanks for any advice you guys might have.

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parts of this sounds like limp mode.

high rpm in neutral doesn't jive w that.

Please explain limp mode. I don't get the high rpm in idle either. stops after a minute though.

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Have your fuel pressure regulator checked.

Oh jeez. Sounds like its time for me to buy more tools. Read the manual on fuel delivery systems. Chapter 7. It might be easier to just buy new filters, new fuel pressure regulator and clean the pump again. Then hope for the best. Fuel pump was cool under all situations so it doesn't seem right to go there. The high idle after shift to neutral is what baffles me.

Obviously the electronic systems are getting involved with compensation issues. Any thoughts out there? Time is of the essence.

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I recently had a loss of power. I replaced the fuel filter, distributor cap and rotor. Got all the power back and it's running great.

Yeah, kind of feel the same way at the moment. Just replace all the things that are getting a little old right now and hope that the problems resolve themselves without further analysis. I could use a new cap and rotor anyway. Probably some new wires as well. And while I am at it maybe a new boat. Just need to keep the wife and kids happy because they are not replaceable.

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Yeah, kind of feel the same way at the moment. Just replace all the things that are getting a little old right now and hope that the problems resolve themselves without further analysis. I could use a new cap and rotor anyway. Probably some new wires as well. And while I am at it maybe a new boat. Just need to keep the wife and kids happy because they are not replaceable.

That's the way...just throw parts at it until you replace the haul. Sooner or later it will run great and look new. :lol:

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That's the way...just throw parts at it until you replace the haul. Sooner or later it will run great and look new. :lol:

Still baffled about the high rpm at idle. Could it be that when the engine is starved for gas under load due to obstruction the ecm sends a signal to dump more fuel into the system and the sensor is to slow to respond after the load is released? A little confused about how quickly the sensors and ecm respond to each other. Should be instantaneous really.

I will be going out to NAPA to get a fuel pressure gauge tomorrow and test the system. If it is the pressure regulator does anyone have a part number for that? Is it an Indmar or is there an appropriate substitute?

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High idle could be the IAC. I just went through a lot with my monsoon. Turned out to be clogged screens on the injectors themselves. Easy to clean. Two Allen screws and the fuel rail comes right off.

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I hope you get to the bottom of this issue...I have the exact same problem. The dealer has had my boat for 5 weeks trying to figure it out. They've replaced the fuel pump, IAC, TPS, fuel filters, and the list goes on. They have done another diagnostic and are sending the data to the techs at Indmar.

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I hope you get to the bottom of this issue...I have the exact same problem. The dealer has had my boat for 5 weeks trying to figure it out. They've replaced the fuel pump, IAC, TPS, fuel filters, and the list goes on. They have done another diagnostic and are sending the data to the techs at Indmar.

5 weeks? Holy &^%%$$#@@!!!!. Our whole boating season here in MT is about 9 to 12 weeks. I am desperate to figure this out quickly. We are 5 or 6 weeks from our first big freeze.

I started with the fuel filters today even though the old ones were replaced 5 weeks ago. Then I inspected the filter in the fuel pump again. Clean as a whistle. Pump was cool when running as well. Went to reinstall the fuel line to the pump and all the threads dropped out like tin foil. It had obviously been over tightened previously. Two prior owners on this boat. Ordered a new pump and had to pay $50 more for expedited shipping so that I might get this done before it snows. Pulled the fuel rails and inspected all the injector filter screens. Clean as well. The manual is wrong on this model year. The injectors do not slide off the rail. They pull out of the rail with O ring seals. Carefully. Re seal with oil on re install. So after staring at the manual and all the different engine models and configurations I could not figure out where the fuel pressure regulator was. The manual says on the port side fuel rail for 5.7L EFI MPI models. Or maybe on the throttle body. Nope. Mounted on the engine on the starboard side just slights above the fuel pump. Just follow all the fuel lines and eventually you will find it. Pulled that sucker and it is not anything like the manual diagram. No filter or stuff to clean. Just disposable. I am about to cross ref the part to see if I can order a new one from NAPA. So that is the saga so far. I will let you know how it ends by Friday.

Oh, BTW I did pull the cap and rotor for inspection. Pretty clean with no corrosion. New plugs 6 weeks ago.

Gremlins in the bilge might be the culprits.

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We can usually boat until October, though it gets cold out, the sun helps. I'm pretty sure that by the time they figure the issue out for me, I will have to tell them to winterize and heat shrink it all up for the winter. Hope you get yours on the water soon! Feelin' your pain.

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TPS? We have a short season here in CO too, feel your pain.

Aren't boats fun?

Wouldn't a fault in the TPS cause problems at all speeds? Not just at 2800 rpms

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Have you checked the throttle cable to see if the momentary high idle isnt your cable sticking? This could be a seperate issue. Do you have perfect pass? If its a voltage problem from the alternator it will cause the perfect pass to turn on and off. This happened to me recently. I know you changed your alternator already though. Strange things can happen when voltage isnt constant. Just something to look at.

I feel your pain too. i just got my boat back after a 5 week alternator change and tune-up.. Im not using that place again.

What type of fuel are you using? Any additives? Have you tried adding some STA-BIL fuel additive? maybe your tank has some bad fuel?

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Have you checked the throttle cable to see if the momentary high idle isnt your cable sticking? This could be a seperate issue. Do you have perfect pass? If its a voltage problem from the alternator it will cause the perfect pass to turn on and off. This happened to me recently. I know you changed your alternator already though. Strange things can happen when voltage isnt constant. Just something to look at.

I feel your pain too. i just got my boat back after a 5 week alternator change and tune-up.. Im not using that place again.

What type of fuel are you using? Any additives? Have you tried adding some STA-BIL fuel additive? maybe your tank has some bad fuel?

Interesting that you should mention the perfect pass. When this was happening the pass was on at first. Then the second the boat started missing, stalling and backfiring I heard the pass beeping on and off and the screen would go temporarily dead. Then I shut it off along with the engine. Upon restart of engine with pass turned off I again accelerated to 2800 rpm with the same result. Even with the pass off the engine starts stalling and the PP screen goes on and off beeping like mad. I assume that if it is turned to off there is no way for it to engage itself. Are you saying that with the pass off and an electrical fluctuation the pass can actually engage itself on and off?

That would be too weird.

It even does this when I have the engine in neutral and I accelerate.

As for gas I seriously doubt it. I filled up at a very busy highway station. I use high octane fuel with no additives. If it was the gas I assume it would do it at all speeds not just 2800.

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For all of you who have tried to help I truly appreciate it. I finally figured it out about an hour before we were going to cancel all our boating plans for the weekend with several other families. Sometimes it is a simple matter of just eliminating one thing at a time in the equation starting with the last thing you touched before the system went haywire.

Drum Roll Please----------it was the alternator. Once I took the brand new alternator out and reinstalled the old one all my problems suddenly went away. All except for having a weak 50 amp alternator again. The one I bought was from DB electrical as suggested in one of the upgrade posts from this site http://www.themalibu...886#entry413886 . This piece of &%$&**()#& should be avoided at all cost. First off due to its increased weight it will break your mounting bracket sooner or later. Mine happened sooner. Secondly, it is so poorly made that it developed a short somewhere inside the casing. And lastly it had a wildly fluctuating output causing all manner of problems that appeared to be fuel related (bogging) but were not. My problem was that it worked flawlessly with a steady output for almost 6 weeks. Therefore leading me to believe that the problem lay elsewhere.

So for all of you who have problems with engine bogging/ backfiring and inconsistent failures that are hard to replicate please take my advice and either swap out your alternator with a loaner (even if it comes from NAPA) if possible or check the output directly. Just know that if you check it directly there is still a good chance it will test fine in your driveway and fail on the water. Luckily these are pretty easy to install. Even in my v drive.

I am now going to rip this thing open to see where and how it failed.

Anyone know of a reasonable place to buy a 70 amp alt? I could have mine rewound but I am short on time and summer is burning away fast.

Hope this helps someone out there..

Cheers

AW

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Thank you for the update on your issues. This is great info for us all.

I'd like to get a high amp output alternator, but will now be very cautuios. Amazing how an alternator can affect performance.

Steve B.

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