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2008 40hp mercury 4 stroke issues

Old 02-14-2020, 09:11 PM
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Default 2008 40hp mercury 4 stroke issues

I have a mercury 4 stroke 40hp motor that I had the carbs cleaned. Ran perfect at the house. Took it out to lake and started right up. Reversed motor and wanted to die. Put it in neutral and revved it up ran fine when I got on step it ran good for 10 seconds then died. Hard to start and had too keep bumping throttle to keep running. Put back on trailer checked for gas leaks and started up and ran fine and runs fine at 1/4 throttle but when I get on step it wants to die. Any ideas
Old 02-15-2020, 06:28 AM
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Carburetors need to be cleaned and adjusted.
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Old 02-15-2020, 06:33 AM
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Very small jets in those carbs. Doesn't take much to clog them you may have cleaned carbs but have crud coming from the tank and or fuel lines. Sounds like the high speed jets are now blocked. Carbs need to come off again.
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Old 02-15-2020, 06:38 AM
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Change the water separator and clean or replace the fuel filter. My 60 hp fuel injected Merc did the same thing. Had water in the gas. Filter changes and new gas solves the problem, that water just doesn’t burn as well😀
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Old 02-15-2020, 10:52 AM
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Thanks I will try again change filter and drain gas. Did notice a little bit of water in gas.
Old 02-15-2020, 05:39 PM
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I would start with a fresh fuel supply in a portable tank/hose combo and replace the fuel filter. It doesn't take a lot of fuel to run on the muffs (no load) but in the water you need full fuel flow. If you are getting water I would invest in a Racor type water separator. There are no name knock offs that work as well for way less money if that is an issue
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Old 02-15-2020, 07:06 PM
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Just pun on new connectors, primer bulb, fuel filter and new gas line in side motor. Will be trying it out tomorrow, and let y’all know how it does thanks,
Old 02-16-2020, 04:45 AM
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How were the carbs ‘cleaned’? If they weren't completely disassembled and soaked, or put in an ultrasonic cleaner, I’d start there.
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Old 02-16-2020, 11:06 AM
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Put new connectors, primer bulb, fuel filter, and water separator. Motor ran great, thanks for all the help greatly appreciated.

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