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2004 mercury 60 hp Bigfoot 4stroke running rough at higher speed

9/15/21 @ 10:10 PM
ORIGINAL POST
Fv.screaming drags.com
Fv.screaming drags.com
USER SINCE 3/29/20

I have a 2004 4 stroke 60 hp fuel Injected mercury big foot on my pontoon boat that will start running rough and almost die at high rpms. Like it's starving for fuel I've checked and cleaned the fuel filter. Replaced the fuel line from the tank to the motor including the primer ball. And also checked all vents for obstructions. After I did all that it ran fine for a couple days but now it is doing the same thing again and I'm stumped. If anyone has had this problem before and or has any thoughts on what could possibly be going on that would be great thanks in advance for any help or advice you can give. 

DISPLAYING 1 TO 10 OF 10 POSTS
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9/22/21 @ 4:20 PM
44/45
MEMBER SINCE 3/9/11

I would also look at the pick up line inside the fuel tank if you have one. It's possible you may only have a nipple on the exterior of the tank. One small piece of debris may be enough to obstruct your fuel flow.

9/22/21 @ 2:42 PM
Fv.screaming drags.com
Fv.screaming drags.com
USER SINCE 3/29/20

Thanks for all the responses and yes it is fuel Injected and has a primer bulb still but no choke 

9/22/21 @ 6:54 AM
Shellfish
USER SINCE 7/19/03

Could be as simple as bad plugs or coil starting to fail.  Try a different fuel tank with fresh gas after you have changed the plugs.  

9/20/21 @ 5:26 PM
TheWhipGuy
USER SINCE 2/13/10

Wjbk95, you have to get fuel to the pump... thats what the primer ball is for. Either way, the bulb has nothing to do with my experience or problem, I just mentioned it, because forcing gas through the obstruction, with the bulb, helped it keep running.

9/20/21 @ 4:05 PM
Wjbk95
USER SINCE 4/12/21

Chopper…marine gas??  I don’t think I’ve ever seen marine gas at any gas station 

9/20/21 @ 4:02 PM
Wjbk95
USER SINCE 4/12/21

And to the whip guy…OP said he had fuel injection, doesn’t that mean no primer ball???

9/20/21 @ 4:00 PM
Wjbk95
USER SINCE 4/12/21

Couple years ago I let mine sit over winter with only a 1/4 tank of gas, didn’t realize till the next spring and after running for a bit had the same problem, changed the plugs and all was fine.  Bad, old gas??

9/20/21 @ 1:21 PM
TheWhipGuy
USER SINCE 2/13/10

I have a 2003 40hp merc bigoot 4stroke on my pontoon.  It was running real rough and eventually would only run while pumping the primer ball.  It turns out the fuel pump black rubber diaphram/membrane was brittle and cracking (probably because of SeaFoam in gas) and wasn't working good.  After replacing the fuel pump, I also removed the fuel line(s) from the output of the fuel pump and up to the injector manifold.  there were chunks of black rubber from the fuel pump clogging the input.  After cleaning the rubber out, it has run great ever since.

9/20/21 @ 3:08 AM
chopper
USER SINCE 7/2/01

Do you always run Marine gas in it?  I didn't and had similar problems when injectors or VST got fouled.

DISPLAYING 1 TO 10 OF 10 POSTS
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