1996 120 hp meercury force

Linnvw

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Aug 31, 2020
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1996 120 hp mercury force that starts rough and only starts will throttle open. Have replaced choke primer solenoid, spark plugs and fuel. Kill switch checks out and I have spark on all plugs. 135 psi compression on each cylinder. What now?
 

Chris1956

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Mar 25, 2004
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Will the motor run at 1200RPM or less? If so, your carbs are likely dirty.
 

Linnvw

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Aug 31, 2020
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Motor will not run below 1200 rpm. What is best way to clean carbs?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Motor will not run below 1200 rpm. What is best way to clean carbs?

follow the factory service manual, take them apart, soak in carb cleaner, chase every passage, re-assemble and adjust per manual.
 

Chris1956

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Mar 25, 2004
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A lot of those motors have high and low speed stator windings. You might ohm them out and make sure both are good.

If the low speed stator winding is bad, the motor will not run at 2000 rpm or lower
 

Texasmark

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Dec 20, 2005
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follow the factory service manual, take them apart, soak in carb cleaner, chase every passage, re-assemble and adjust per manual.

After all the cleaning Scott recommended, get your 100 psi air compressor and blow everything out real good. One little black speck of deteriorated fuel line was obstructing the high speed jet on one of my 3 carbs once upon a time, and causing my engine problems. Had I not used the air, I never would have seen it and all my work would have been for naught.
 

Texasmark

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Dec 20, 2005
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14,896
A lot of those motors have high and low speed stator windings. You might ohm them out and make sure both are good.

If the low speed stator winding is bad, the motor will not run at 2000 rpm or lower

Since you mentioned this, did you ever read up on/hear of why Merc. does that? I know they use pickup coils for battery charging, another set for triggers, and another set to get voltage to charge the energy storage capacitors in the ignition system, but why 2 sets of coils and which are they, the capacitor charging coils? What's the point?
 
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