Yamaha stall out when advancing throttle

[tom2770]

2003 70 Hp Yamaha will stall out when advancing throttle.All carbs were removed soaked in carb cleaner washed and blown dry with new kits.Compression is 124 lbs on all cylinders with good spark and fuel.I noticed if i hold my hand over the intake of carbs 2 and 3 there is very little suction and has little effect on how the engine runs.If I hold my hand over cylinder 1 it will stall out the motor. Also if i pull the wires off of cyl 2&3 it has little effect on how the motor runs. I also noticed that sometimes if i punch the throttle repeately the motor will take off and run fine at 5500-6000 rpm w.o.t untill i shut it down and try to restart it. Hope you can help,it's driving me nuts.Thanks for your help
Tom

 

[nykile220]

Re: Yamaha stall out when advancing throttle

I have a 50 hp yamaha 2003 that feels like it has no power when trying to accelerate. will noy happen everytime but when it does it's hard to get on plane. runs fine once i overcome the hesitation.

 

[James R]

Re: Yamaha stall out when advancing throttle

Need to check the fuel availability. Start the motor and spray a 50:1 fuel mix into each of the suspect carb intakes. If the motor picks up you have a carb or pump problem. Checking the compressions and sparks is essential in diagnosing the problem.

 

[GrayBlue]

Re: Yamaha stall out when advancing throttle

How old is the gas? Do you have a water separator? If so does it need replacing? Have you checked the spark plugs? What do they look like? Are you sure the carbs are clean? What's the history of this motor? Have you owned it a while or is it new to you?

 

[nykile220]

Re: Yamaha stall out when advancing throttle

How old is the gas? Do you have a water separator? If so does it need replacing? Have you checked the spark plugs? What do they look like? Are you sure the carbs are clean? What's the history of this motor? Have you owned it a while or is it new to you?

The gas is new. I just replaced the spark plugs. The carbs were recently re-built. I run the motor often and I have had the boat about 2 yrs.