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4.3 mercruiser wont shut off

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ckneifl

New member
when i am on the water and shut the enigine off it deisels, or wont shut down right away, sumtimes i rev it up then it dies but eventialy it will die, i have ran a couple of tanks of gas through it, even different brands, i bought some seafoam to try this weekend, any suggestions on what else i should do, plugs?cap?rotor?
 
Idle speed too high????(Most likely cause) Normal operating temperature??? Wrong heat range of spark plugs??? Have you tried high test???
 
it idles perfect, i did notice last time i had it out the temp guage never came off of cold, i have ran the same plugs for the last couple years. have not tried high test.
 
ckneifl said:
it idles perfect, i did notice last time i had it out the temp guage never came off of cold, i have ran the same plugs for the last couple years. have not tried high test.
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idle should be 700 rpm or less. the run on can be caused by incorrect timing ..if the thermostat is stuck open this may create carbon deposits causing this condition ..

pull plugs see what they look like..if heavy black deposits on tips could even be mixture screws or other carb problems.


higher octane is not the cure for this . you never used the high octane before correct ?


seafoam when used at the proper amounts helps clean out the fuel system ..have extra fuel filters ready..
 
Check the timing, change the plugs, make sure the throttle (not the choke) closes when the engine is turned off, decarbon the engine w/the SeaFoam and add a can to the gas tank.
 
sometimes dieseling is the motor running backwards. And if that happens you can draw water into the motor.

You let it idle for 4-5 minutes before you shut down the motor ? That alone may fix your problem.

Whats your oil look like ? There is a reason for the question !

The plugs look like what ?

Spark Plugs
 
the plugs look like they are burning good, no soot, no carbon on them, the porcelin is white with just a little tarnish to it. oil level is good, but this is my third year on the oil.
 
ckneifl said:
the plugs look like they are burning good, no soot, no carbon on them, the porcelin is white with just a little tarnish to it. oil level is good, but this is my third year on the oil.
Click to expand...

the plugs color white may mean the timing is too far advanced ..make sure the timing is correct ..

plugs should be light brown with a slight amount of deposits..plugs that are too clean too white could be more than timing issues..
 
i gave him the site to see what they look like in all conditions , so i have to think he went to the site and checked it out.

Maybe you guys can help him.
 
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