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40HP 4 STROKE MERC RUNNING PROBLEMS

Discussion Forum at MarineEngine.com » Mercury Mariner Outboard » Archive through July 25, 2009 » 40HP 4 STROKE MERC RUNNING PROBLEMS « Previous Next »

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Dave A
New member
Username: danger

Post Number: 1
Registered: 07-2009
Posted on Tuesday, July 21, 2009 - 10:58 am:   Edit Post Delete Post View Post/Check IP

Have a 2000 40hp idles good and off idle is good.at about 1800rpm starts to flutter and gets a little rough,this is when under load.If deacel fast engine stalls, if back off easy won't stall.Sometimes alarm will sound and its off right then.Have changed plugs no signs on them of anything,have checked for fire at the wires has good spark,(but can't get to engine while under load so all these test are done sitting still).This all started after oil change and winterwized.Looking for some help?
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Graham Lamb
Senior Member
Username: galamb

Post Number: 5767
Registered: 05-2007


Posted on Tuesday, July 21, 2009 - 12:01 pm:   Edit Post Delete Post View Post/Check IP

A stall on fast deceleration is sometimes caused by a sticky/dirty float valve - doesn't close as quickly as you back off the throttle and you flood out the motor.

When the motor was winterized if you didn't pull the carb(s) and empty the bowls completely, you can get "cooties" :-)

It doesn't sound horrible yet, so I would try simply running a good dose of SeaFoam (or any other Marine additive that is supposed to clean gunk/carbon out of the system) mixed with the gas first - you may get lucky and it will flush it out if that's the problem.

At the worst, it will still clean up your motor a bit (a good thing)....
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Graham Lamb
Senior Member
Username: galamb

Post Number: 5768
Registered: 05-2007


Posted on Tuesday, July 21, 2009 - 12:12 pm:   Edit Post Delete Post View Post/Check IP

Sorry - mind was wandering there and missed the part about the engine "fluttering" or hesitating around 1800 (no load) - definately sounds like carb cooties - jets and the float valve.

I would still try the Seafoam first..
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Dave A
New member
Username: danger

Post Number: 2
Registered: 07-2009
Posted on Tuesday, July 21, 2009 - 12:17 pm:   Edit Post Delete Post View Post/Check IP

I will give it a try, anything better than pulling the carbs to start! Thanks again will let you know.

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