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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10618
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have an Evinrude 1992 V4 120HP VE, The motor starts fine

Customer Question

I have an Evinrude 1992 V4 120HP VE, The motor starts fine 1-2 crank cold and starts I have changed the Plug recently and the oil gas mix is fine… I run it 55:1…. The motor runs fine at mid RPM but if I open it at first it runs fine but after 5-10 minutes it starts to miss fire and jerk at high RPM… this makes a stressful ride what could it be I have a video of the motor running and doing it…
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.
Hello. My name is***** post the video. Do you have a timing light to check the spark when the engine is acting up?
Customer: replied 1 year ago.

No I am not equiped to do so... will post the video...

https://youtu.be/uslHHhib2hg

Expert:  Tan replied 1 year ago.
Ok that is an ignition misfire. This is usually a failing ignition coil. This is the reason for the timing light to determine which cylinder is misfiring. Now the other option you have is to get an ignition coil and test it on each cylinder to see if you can find the failing ignition coil. There are 4 coils on this engine. So what would you like to do since you don't have a timing light?
Expert:  Tan replied 1 year ago.
There is other possibilities you have a bad ground on one of the coils or a bad spark plug wire. Then if this doesn't solve the issue it is going to be a bad power pack. The timing light will narrow down the issue the best but swapping the coils out with a new coil is next. Post back if you need further assistance. Thank you..........Tan

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