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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10598
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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1989 Yamaha 40 hps, 2 stroke, 3 cylinder motor. How do you

Customer Question

1989 Yamaha 40 hps, 2 stroke, 3 cylinder motor. How do you adjust the motor so it will idle at a low speed. It run well when it is in high speeds. If you would like to call me to talk, you can call me at(###) ###-#### If you don't get me, leave a message and I will call you back. Thank you, ***** *****
Submitted: 2 months ago.
Category: Boat
Expert:  Jason replied 2 months ago.

Hi Jerry, good morning my name is Jason.

What is the model number on this engine?

Customer: replied 2 months ago.
Yamaha 40 SG 6H4 S 181691 only number on the motor
Expert:  Tan replied 2 months ago.

Hello Jerry. My name is Tan.

Have you tried adjusting the idle jets? If no start out with a setting of 1.5 turns from lightly seated. Then put engine in the water let engine warm up. Now fine tune the jets till you achieve the best idle. Turn CW to make leaner or less fuel and CCW to make richer more fuel.

The idle jet is on the top of each carb stbd side with the slotted srew and spring.

Post back with findings and questions.

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