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7.4 Bogs down and dies after sitting!

Mercury MerCruiser

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Old 07-06-2015, 12:21 AM   #1

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Default 7.4 Bogs down and dies after sitting!

I've got a 96 272 Mariah with a 7.4L. It starts great off the trailer and we drive it for a while then sit in a cove for an hour or three. The boat will start right back up and idle fine. As we leave, I open the throttle and it starts to plane out. It will stall out and die every time like clockwork. It starts right back up with a turn of the key. It will the run like a new boat as long and as hard as you want to go. Can't make it miss or chug any other time. There is no water in the tank, and new fuel filter. The carb was rebuilt last summer, new fuel pump last summer. New coil this season. Any ideas? My next move is plugs and wires.
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  • Old 07-09-2015, 10:22 AM   #2
     
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    Default Re: 7.4 Bogs down and dies after sitting!

    Sounds like the accelerator pump on the carb.
    Probably the secondary pump if it's transitioning from tick over to throttle ok but bogging under heavy load as you're trying to get over the hump.


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    Old 07-09-2015, 11:28 AM   #3
     
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    Default Re: 7.4 Bogs down and dies after sitting!

    Possibly getting vapor lock in a fuel line? You hammer it, the vapor bubble gets pushed into carb bowl causing a stall. You crank it until carb bowl fills and all is well. Have you ever tried leaving your motor hatch open while coving?

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