91 Mercury 100 won't run past about 1800 rpm

bikerider

Petty Officer 2nd Class
Joined
Aug 20, 2012
Messages
144
I pulled the spark plugs out and took a picture. These have about 30 minutes of run time on them and were changed after first time I could not get the boat to go above 1800-2000 rpm.

Edit: #1 would be the very top spark plug as they sit in the motor.
 

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racerone

Supreme Mariner
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Dec 28, 2013
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The bottom 2 cylinders should SPARK all the time.-----The bottom 2 carburetors do not work below about 1800 RPM>
 

bikerider

Petty Officer 2nd Class
Joined
Aug 20, 2012
Messages
144
The bottom 2 cylinders should SPARK all the time.-----The bottom 2 carburetors do not work below about 1800 RPM>
Is there a way to test if I have two bad coils or a bad high speed stator winding?
 

Dave1027

Lieutenant Junior Grade
Joined
May 25, 2010
Messages
1,080
Is there a way to test if I have two bad coils or a bad high speed stator winding?
I'm a little confused. You stated earlier you don't have spark on the bottom two cylinders. That would definitely cause your motor not to rev past 1800 in the water.

But why are your bottom two spark plugs so black if they have no spark? They would be wet but clean if that was the case. I'm thinking you are getting spark at some point on those. But those two cylinders are possibly saturated with fuel/oil so it won't burn off.

Tell more about the 30 minutes on those spark plugs. Was it idling? Full throttle?
 
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