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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3710
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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My 125 elpto seems to be only firering on

Customer Question

my 125 elpto seems to be only firering on the top to cyliners at 2000 revs motor seems ok at full stick gets 2700 revs and chokes.
Submitted: 1 year ago.
Category: Boat
Expert:  Charles replied 1 year ago.

Hello, my name is***** will assist you today.

Do you have spark on the bottom two cylinders when you get above 2500 RPM? You can use a timing light on the plug wires, and just watch the flash to see if there is spark.

Customer: replied 1 year ago.
dont have a timing light took plugs out all had spark but seemed week no.3 looks like it hasnt fired a shot no.4 hardly ever top 2 look like they were doing all the work when tested on water will rev to 4500 easy using throttle when in gear only 2700 except a couple of times it reached 4500 but only for a few seconds. cheers john
Expert:  Charles replied 1 year ago.


Your engine is what is called a 2+2. It will idle and run on 1 and 2 up until about 2500 RPM, then 3 and 4 come is and help make the power. Has your engine been sitting for some time?

Have you checked to make sure that there is no water in the fuel?

Also, what is the compression on the engine?

Customer: replied 1 year ago.
purchased recently the boat has been sitting for a while preavious owner had full service done new filters plugs oil etc no water in fuel comp. 125 on all cyl. 70 hours on the meter I fitted fuel pump kit thinking that was the problem vents working I hooked up a plastic tank fresh fuel strait to motor with no change in performance.
Expert:  Charles replied 1 year ago.

With the boat sitting, the fuel in the carbs evaporates, leaving behind the oil and a varnish. This would clog the jet and the tube in the carb bowl. Pull the rain screw from 3 and 4 carb. If it is gummy or green looking, you will need to clean the carbs. They come off as a unit, so might as well as look at all 4.

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