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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4728
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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Is there any way to remove the low speed circuit so it would

Customer Question

Is there any way to remove the low speed circuit so it would run on all 4. About 2600 rpm my 125 goes from firing on 2 cyls to all 4. It is on a pontoon and we have a hard time taking a slow ride?
Submitted: 2 years ago.
Category: Boat
Expert:  Jeff G. replied 2 years ago.
The problem isn't removing the low speed circuit it is the other two carburetors not having a proper low speed circuit. To remedy this you would need to totally replace and rebuild two carbs, not cheap or efficient.You may need to have the motor tuned, de-carboned or deposits in the engine and the idle speed raised a little bit. I would make sure the tech who is doing the work can do it with the engine in the water or in a test tank.Your engine is a bit complicated, fuel system wise and if not in proper tune and linkage sync just right can be a problem. Not the best idea a manufacturer has come up with.
Customer: replied 2 years ago.
Can the speed for engine running on 2 cylinders be adjusted up or down? In others words can the rpm for the 2nd set of carbs be adjusted up or down?]
Expert:  Jeff G. replied 2 years ago.
The idle speed for the engine as a whole can be adjusted. The only thing to adjust on the carbs with the idle circuit is the idle mixture. The carbs without the idle circuit do not have an adjustment.Do you have a tachometer on the boat? If so what is the idle rpm?
Customer: replied 2 years ago.
600 rpm is what it idles at
Expert:  Jeff G. replied 2 years ago.
Can I get the serial number of the engine?
Customer: replied 2 years ago.
Yes I do have a tach
Customer: replied 2 years ago.
It is a 2001 125hp #DT319620
Expert:  Jeff G. replied 2 years ago.
Your idle speed in gear should be 675 +- 25 rpm. So your idle speed is too low. At the very bottom of the throttle arm is the idle stop screw. Loosen the jam nut slightly and turn the screw in just slightly to raise the rpm. Do this with the engine in the water in gear under load. If you have good cleats on the boat and dock you can just tie off the boat.Do this adjustment with the cable off the throttle arm. After achieving the desired rpm, in your case close to 700 rpm, then adjust the throttle cable to align with the attachment points.Does this make sense to you? BTW the serial number it OT not DT just for future reference.