2002 yamaha 115hp 2 stroke

[Adam D]

This is a new boat to me. Seems to be skipping at ldle. Upon starting it back fires then idles. All the plugs have decent spark, Changed the fuel filter, checked the lines. Everything looks good. The boat seems to run fine when I give it gas. The shake at idle just seems to much. Any ideas what I should do? Thanks

 

[Herman Melville]

The idle governed by the following things:

1) The idle jet inside the carb. This is tiny tiny tiny and can get blocked. - Carb ultrasound clean and re set it up correctly.
2) The idle mixture screw on the carb - a needle valve that needs to be clean - Carb ultrasound clean and then set them correctly.
3) The vacuum on the inlet manifold is imprtant on idle - balance the carbs once cleaned.
4) Any vacuum leak after the carb throat on the intake - any kind of crack / not sealing gasket etc... anbd this will cause problems. You would be surprised how small a leak it takes......
5) Once all sorted above use the idle screws on the carbs to set the idle to suitable rate.

Make sure your gas is fresh too.