2005 Mercury 5 litre MPI wont idle

poky1234

Cadet
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Jul 5, 2016
Messages
7
Hello,

I have a 2005 Four Winns Horizon 200 with a Mercury 5 Litre MPI engine. The boat wont idle. I can get it running and into gear quickly and it then runs normal, no hesitation issues. When I pull it back down to idle it stalls. Changed the fuel filter, no change. Marina says fuel pump is bad and they have to pull engine to replace fuel pump. I dont understand why it would be a fuel pump when it runs great once you get the rpms up. Any comments would be appreciated.

Thanks
 

poky1234

Cadet
Joined
Jul 5, 2016
Messages
7
replaced IAC today. boat is now idling fine. Thanks AllDodge.

Has a high pitched whine though. Any idea on that? What should the fuel pressure be?

Thanks.
 

alldodge

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Mar 8, 2009
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A sound is hard to identify from a laptop. Is the whine constant or does it increase as the rpm's increase? How is the outdrive lube bottle?
 

poky1234

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Jul 5, 2016
Messages
7
I'll check tomorrow and see if the whine increases with rpm. I will also look at outdrive lube bottle.

Thanks.
 

poky1234

Cadet
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Jul 5, 2016
Messages
7
Sorry for the delay. High pitched whine does not increase with rpm and outdrive lube bottle looks 3/4 full.
 

alldodge

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Since it doesn't change with rpm it ay not have anything to do with the motor. Is the engine blower on, or maybe a bilge pump?
 

alldodge

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no , none of those things as I would still hear that with engine off, key on.

I would think then it should be easier to find. Key on and start looking around for what is running. Maybe the fuel pump, but the fuel pump should only run for a few seconds and then shut off with the motor not running.
 
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