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454 MAG Quits When Running Wide Open But Starts Back Up???

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Old 06-12-2009, 11:18 AM
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Sound like a simple fuel issue. You have a restriction somewhere. Filter, needle valve(s) in float bowls, or weak pump. It shuts off when it runs out of gas. You are starving the engine. I would start with the filter and or water seperator and then the carb. Loose wires would not only happen at WOT. If it were popping and sputtering I would guess ignition, But the way you describe it is running out of gas.
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Old 06-12-2009, 12:47 PM
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Do you have a kill switch and if so is it adjusted right?
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Old 06-15-2009, 08:01 AM
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I checked the screen where the fuel line goes into the carb. and there was nothing in it. I started the boat and wiggled the harness all over and couldn't get it to act up. I took the boat out again after that and ran it about 15 minutes and then it quit at cruising speed this time. It ran fine until it quit. It would barely start back up and skip and backfire and hardly run and then stall. If I let it sit a few minutes it would start but I couldn't keep it running long and when it did run it barely ran. I was trying to limp it back to the launch idling but I couldn't keep it running for long. After about an hour of this it seemed like it was healing up and it idled for quite awhile so I decided to try opening it up a little. It ran fine all day long after that without any issues at all. I am totally stumped on this one? I was thinking water in the gas now. I was going to pull of the twist on fuel filter and see if there was water in it. Any other ideas? The problem seems to be happening more often and this last time was the first time the boat made me think I wasn't going to make it home without a tow. Thanks again for all the help!
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Old 06-15-2009, 08:02 AM
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I'm running the stock carb. and the kill switch is not hooked up (I know it should be and it will be soon.)
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Old 06-15-2009, 08:04 AM
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I was thinking a weak fuel pump and I thought it had finally gone bad this last time when it wouldn't even idle but then it healed up so I doubt a pump would do that right? Previously it had only had issues at wide open throttle and it always started right back up. This time was different it wouldn't even stay running at idle for awhile.
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Old 06-15-2009, 08:18 AM
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I have seen fuel pumps act up.
Time for a fuel pressure guage and some spark Diag equipment.
Local shop?
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Old 06-15-2009, 10:52 AM
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You have a fuel problem that is getting worse. You are going to hurt the engine if you keep driving it. Take the carb apart and clean it. Change the filters. Hook up a fuel pressure gauge and see if the pump is failing. Or take it to a mechanic.
Do not drive the boat any longer. I think it is the carb.
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Old 06-15-2009, 12:43 PM
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Quote:
Originally Posted by Brad Zastrow View Post
You have a fuel problem that is getting worse. You are going to hurt the engine if you keep driving it. Take the carb apart and clean it. Change the filters. Hook up a fuel pressure gauge and see if the pump is failing. Or take it to a mechanic.
Do not drive the boat any longer. I think it is the carb.
Hey Brad
Quit reading my mind!!!
What he said too!
Thump
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Old 06-23-2009, 11:10 AM
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I was told if the fuel pump is bad I should see gas in the small clear line that runs from the pump to the carb. is that right?
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Old 06-23-2009, 11:42 AM
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No not always, that is if the pump has ruptured not if the function of the pump has diminished / loss of pressure. time for a guage
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