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1999 Mercury 250 EFI Outboard

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EFI

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Have a 1998 mercury 250 EFI outboard. sat for 5 years cleaned the injectors fuel filter clean rec fuel. Engine runs great at high speed on the lake but wont idle down below 1200 rpm. took it to a
mercury dealership to have it diagnosed and said they cant bring the idle down any lower. workshop manual says it should idle @
750 rpm. wondering if it's a vacume leak leaking injector or the TPS. butterfly's seem to be closed and checked the linkage all in specs. Can you help me since the mercury dealership in Jackson cant...........Fustrated EFI. :mad:
 
Make sure your throttle plates are closing completely.

If they are, then....

You will need a timing light with a tachometer set to 2cycle. Start the engine, let it idle, Attach the timing light to a plug wire and check the RPM, do this for every cylinder. Make sure they are all reading the same....
 
faztbullet said:
How did you clean injectors? With a pressure pulse injector cleaning kit which you hook up to twelve volts and test each one at a time . They all seem to have the sane spray pattern. Do you think a leaking injector or a vacume leak ? Replaced most all the vacume lines also
Click to expand...
 
EFI said:
Have a 1998 mercury 250 EFI outboard. sat for 5 years cleaned the injectors fuel filter clean rec fuel. Engine runs great at high speed on the lake but wont idle down below 1200 rpm. took it to a
mercury dealership to have it diagnosed and said they cant bring the idle down any lower. workshop manual says it should idle @
750 rpm. wondering if it's a vacume leak leaking injector or the TPS. butterfly's seem to be closed and checked the linkage all in specs. Can you help me since the mercury dealership in Jackson cant...........Fustrated EFI. :mad:
Click to expand...

I had the same problem with my 2000 150. It was a small leaf caught in the buttery fly valve. Make sure your butterfly valves are opening and closing all the way.
 
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