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BOAT RUNS FINE THEN LOSSES POWER????


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First of all I would like to say hello to everyone I am new to the site.

I need some help diagnosing my boat's problem. It is a 2004 VLX.

Last year at the end of the season the boat started running bad after running it for about 30 min. I could shut the boat off and let it sit for 5 min and it would run again fine for about 5 min. then it would lose power again and would backfire when I tried opening the throttle. Well I put a new fuel filter on it and that didn't fix the problem. After that I put it up for the winter.

I read on this forum about cleaning the filter on the inlet of the fuel pump so I pulled it off Wed. and cleaned it. I took the boat to the lake yesterday and rode around the lake for 15 min and the boat ran great. Then I filled the ballast and launched it a couple of times and it ran perfect. I drained the ballast and rode again for about 15 min then repeated with filling and launching again. After all of this I was on cloud nine because the boat was running great. So I headed to the boat ramp after a great run and then it happened, I was running about 43 mph and I watched as the boat started losing speed. I was freaking out. So I made it to the boat ramp dropped my buddy off to get the truck and I went out of the wake zone and punched it (throttle not the boat) and the power was back!!! I never turned the motor off, I just pulled to the dock and idled for a min. I must also add that when the boat started running bad I went and listened to the fuel pump and it was making a whining noise.

I read on here that people have had to put cold rags on their fuel pumps to cool of the pump to get their boat running again. Maybe this is that. But I need help if any of you have suggestions. Plus I want to update it when I do get it fixed so others with this problem can benefit. Ill be the guinea pig.

Thanks in advance, :)

Matt

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There are so many people having this problem its not funny. I have the exact same issue and I have replaced one fuel injector cleaned and replaced all the filters. The Dealer is currently pulling all the injectors out again to clean the filters on the tops of the injectors thinking they could be clogged. There are really small filters in the tops of the injectors just like the one before the fuel pump. Who else is having this issue?

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I must also add that when the boat started running bad I went and listened to the fuel pump and it was making a whining noise.

Your fuel pump whining or squealing is the key here. Your fuel pump will whine or squeal for two reasons.

One, it's starving for fuel. These pumps use the fuel to lubricate themselves, and a blocked filter (at the pump or your 'regular' fuel filter) will cause this to happen. Makes the same (or worse) sound as when you first turn the key on and the pumps primes itself.

Two, they are in the early stages of failing. Some of these pumps seem to last for years, some for less than a season. Luck of the draw, I suppose.

But it sounds like you have ruled out the fuel starvation, so I would say that you may have a fuel pump going bad.

One more note: There is a metal screen type filter on the bottom (inlet side ) of these high pressure fuel pumps. I've had mine get a piece of debris stuck in there and it produced the fuel pump squeal and performance issues intermittantly (I guess when I turned the engine off the debris would 'sink' down the fuel line, only to be sucked back up after the engine was started.). Have you checked that out? Just disconnect the fuel line from the bottom of the pump and use an inspection mirror to look in there and see if there is any junk.

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You can replace the injector filters yourself, the master mechanic where I used to work actually came up with the procedure and it lead to a tech bulliton from Indmar.

You have to pull all the injectors, and on an 04 VLX with a monsoon that means also pulling off the plenum. You then take a #10 srew and use it to pull out the screens from the top of the injectors (just a press fit). Push in new screens and then reassemble. Takes an our or so, add a bit more if you're pulling the plenum. Just be careful not to drop anything down the injector holes, or you'll be pulling off the intake to retrieve it.

It is a weird problem though, I've seen boats with 50 hours with screens so dirty its amazing the boat ran at all, and I've pulled screens off boats with 1300 hours and the screens were clean as a whistle.

-Chris

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i think ethanol issues are started to pop up more and more. that is why i am now running startron in both my boats, plus Yamalube in the outboard.

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I put fresh gas in my boat everytime I use it for this reason. I would say at any given time I have no more 10 gallons of older gas and always put atleast 5 more in.

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I have cleaned the screen in the fuel pump but I think I will do it again just to see if it has clogged again. I will have my friends dad look at the injectors as he is a mechanic and I would hate to mess anything up. Do any of you think it could be a vapor lock issue? Where could I buy a new fuel pump from??? Thanks again guys!

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vapor lock is typically on very hot days when the boat is shut down. No way you vapor locked at WOT as there is ample fuel flow in the rail to prevent the fuel from boiling.

Skidim.com or a dealer is the best place to get a pump.

-Chris

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Thanks! I forgot to mention in my orginal post that the motor is a Monsoon 340.

Does anyone think that this could be an issue with the coil???

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This could be a computer related problem, if ignition timing is changing at higher rpm's it would feel the same way. You need to put a diagnostic machine to see if you fuel ratio and timing are effected during the loss of power and this should be done on a water test drive.

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Sorry to sound so inexperienced but where can I get a diagnostic tester?

I'm not sure about our boats, I think they are OBDI based PCM's. I'll talk to my friend and see what is available, but it's going to cost some $$$ fuel ratio has to be checked with a narrow band O2 sensor that is hooked up to the exhaust (not exactly sure how you do it on a wet exhaust system, but I'm sure they are available). As long as you have good fuel pressure and the plugs don't look white indicating a lean condition I think all you need to do is hook up a timing light to make sure your timing is not jumping around and those you can get at any parts store for less $40. The other thing is ignition output which again can be checked by pulling plugs but you need to run the engine for a while in the "lossing power condition" then shutting the engine down as soon as you can and pull some plugs to see what color they are. If your looking spark you'll be running rich which will feel like loss of power but actually it's bogging down and flooding.

Have you checked your ignition module or replaced that to see if it runs better?

Edited by 68Slalom
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I have not. This is the first I have read about the ignition module.

Have you hooked up a fuel pressure gauge up to see if you holding pressure?

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Yes the guage was hooked up while the boat was running fine and was out of the water at my house. So im not sure that would be the same as when it is running poorly.

I have a gut feeling it is related to the fuel pump. Because when it starts acting up I can let off the throttle and it tries correcting itself but If I gag it, it starts backfiring and trying to bog.

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Yes the guage was hooked up while the boat was running fine and was out of the water at my house. So im not sure that would be the same as when it is running poorly.

I have a gut feeling it is related to the fuel pump. Because when it starts acting up I can let off the throttle and it tries correcting itself but If I gag it, it starts backfiring and trying to bog.

Yeah, I would keep the gauge hooked up and see what pressure you have when it starts to act up. Running it in the driveway is much different than when you have a load on it and it's demanding much more fuel. Your compression raises by almost 20% under a loaded condition.

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I have not had this problem with my current boat however this sounds like the exact problem I had with my previous boat that had a mercruiser - backfiring and losing power sometimes. I replaced and cleaned everything in the fuel system and still had the problem. It turned out to be the ingition module. It was sporadic and then it finally quit for good and left me stranded and had to get towed in.

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I had the same problem you mention. Just like you said when the boat started booging down the pump started to whine. When I cleaned my screen filter I also took all the fuel hoses off all the way back to the tank. Since I did both at the same time I could have had something in the line that I did not notice when I cleaned the filter. So I would pull all the hoses going from the tank to the fuel pump and just blow everything out of them, clean the screen again and give it another shot.

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Mine holds 40psi at idle and even at full throttle when the engine starts losing power its still at 40psi.

So you have good pressure, the only other two sources are vacuum and ignition. Does the engine miss at all at idle?

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Will do. By the way does anyone know the part number of the ignition module?

You could call the dealer and they should know right away, there is a way to test them if you have a qualified mechanic. You test it in volts and ohms, it may be faster just replacing it than finding someone to test yours and then your boat is down until you get the part back.

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