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Mercury 125 Optimax 1.5L keeps missing mostly at lower rpms

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k_emarine

Member
I have a 125 Optimax that keeps cutting down to what I think is two cylinders. I replaced the fuel injectors and pulled the electric fuel pumps out and cleaned the vst activated the fuel pumps and circulated a cup of fuel back and forth with them. When the motor runs for a few minutes it drops down. If I spray a little fuel in the intake the motor seems to pick back up. Any input would be greatly appreciated.
 
Now it will hardly start unless I accelerate the throttle. If I lower the rpms to around 1500 it will still run for a few minutes and then run out of fuel. If I spray fuel in the intake it will continue to run. I took the entire VST off of my brother in laws motor and the motor did the same thing. Input please!
 
You are going to have to do a Leak Down test on this engine before you do anything else. Not a compression test, a leak down. If it passes the leak down we can move on from there.
 
I will see what I can do. The boat is in the water now and trailer has another boat on it. I will update when I get that checked. Thanks!
 
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