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Old 09-12-2011, 10:33 AM   #1
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Unhappy engine cutting out about 3000 rpm's

Greetings,
Had a problem yesterday after running about 30 minutes at 3000 rpm's in calm seas. Boat ran fine then started to sputter and die out. Befor it stalled I pulled back the throttle to idle then slowly increased for a few minutes. I then increased it back to about 3000 and after a few minutes the same thing happened. made it back to slip doing this about 3 times. Runs great at idle all the time. Suspect water in gas as boat was not registered for two years and tank was full. Will add fuel treatment and top off tank (now about 3/4 full, and change fuel filter. Anything else I should look for ?
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Old 09-12-2011, 01:00 PM   #2
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Blocked tank vent, after running for a while you are creating a vacuum in the tank and the fuel pump can't overcome it. Just my guess....
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Old 09-12-2011, 01:25 PM   #3
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Read this post CC, especially #22. http://www.maxumownersclub.com/forum...High-RPM/page3

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Old 09-12-2011, 11:46 PM   #4
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thanks for your input; I'll check it out.
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Old 09-14-2011, 11:05 AM   #5
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Thanks to those who offered help here. I checked the vent tube and all seems clear. I have added some additives to remove water and refresh the gasoline in hopes that this will cure the problem. We'll see . I am down to about 1/2 tank (25-30 gallons) remaining in tank so I'm not sure if I want to try and just burn it or dilute it with fresh fuel. Any thoughts on this?
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Old 09-14-2011, 12:41 PM   #6
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Quote:
Originally Posted by ccruser1 View Post
I am down to about 1/2 tank (25-30 gallons) remaining in tank so I'm not sure if I want to try and just burn it or dilute it with fresh fuel. Any thoughts on this?
This is sort of a toss-up. It's late in the season and the fuel is not going to get better with age. I prefer to leave the tank full to reduce condensation, but folks seem to be split on this theory regarding leaving the tank full or empty. I wouldn't expect bad gas to cause a situation where the boat starts, idles and runs strong up to 3,000 RPM, then dies completely. I would expect it to run poorly, however. That is not what it sounds like though. If the gas has sat for two years, I would consider getting rid of it.

Is this a carb or fuel injected motor? What year is the motor?
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Old 09-14-2011, 01:51 PM   #7
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I gotta say that at this point I soooo don't think it's bad gas. If at all possible I'd remove the vent tube from where it connects to the top of the fuel tank, remove the fuel fill cap, and use compressed air to blow through the vent line from the tank side to the fill side.

Regardless, a very quick way to find out if it is vent related is to run the boat and when the symptom appears immediately loosen the gas cap - if at all possible when the engine starts gasping. Or, while the gas level is low, loosen the cap a turn or two and use a piece of tape across it so that it doesn't loosen further - then go run the boat.

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Old 09-15-2011, 12:17 AM   #8
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this is a carb on a 4.3 v6. I was able to remove the vent tube and blow easily thru it. Air could be heard escaping thru the vent cover so I know it is clear. It starts right up and runs well for first half hour then it cut out and was run back to slip thru channel at low speed. Was able to put in nuetral and shift into reverse for docking into slip without engine cutting out. Have not checked electrical yet but not thinking this is where problem lies. Any thoughts?
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Old 09-15-2011, 12:58 AM   #9
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What year? It's got to be fuel or spark...... I'll still bet fuel but your there and I'm not.
Depending on year... you may have a bad ECM or coil..... I had a coil once that would get hotter than.... you know, and start cutting out, especially at higher RPM's.
Normally, in my experience anyway, ECM's just quit and you get nothing as far as spark.
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Old 09-15-2011, 10:35 AM   #10
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this is a 93 so it has a coil. I still think it is fuel related because of the fact that even after it is hot it runs well at lower rpm's.
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