1995 Yamaha 175

Friends boat has been sitting almost 2 years. Rebuilt the carbs, drained as much of the gas as we can get out. Refilled with 97 octane and octane boost. Got the engine running. Ran 5 gallons, changed the filter. Got some water out. Ran another 10 gallons still getting water. All and all the engine runs ok except at idle. Has a tendency to cough or backfire then stall. I know there are still fuel quality issues, does this sound fuel related or should I be looking at the ignition/timing? Plugs are new, wires look ok.

 

Its sounds as though its just running a bit weak or possibly too slow.

Is there some mixture screws you could tweak?

 

Yes it has 3 two barrel carbs. Each has a mixture screw. They are all supposed to be opened the same amount. I have them about middle of the suggested adjustment range. If parked down wind when it coughs, the exhaust smells rich, hate to open it up too much more. Idle has been adjusted to about 700. Range out of gear is 650-725. Hate to go too much higher because it slams into gear.

 

Too lean

Finally found a mechanic that would talk to me. He said throw out the book values for the mixture screws. Open them 1.5 turns and adjust from there. I do have the motor running too lean.