99 Yamaha OX66 250 Won't Accelerate After Idle

[Control3391]

Recent owner of 99 Yamaha L250X. 300 HRS Engine runs fine most of time but after idling at the ramp or while slow trolling, the motor will not accelerate back to speed. If you put the engine in reverse and throttle up for several moments and then return to forward gear, it runs fine. Just replaced all three low presure fuel pumps and plugs. Any suggestions? No fuel leaks that I can detect.

 

[rodbolt]

Re: 99 Yamaha OX66 250 Won't Accelerate After Idle

check the shift cut switch, if it stays triggered it will keep certain cylinders cut, also check the fuel rail pressure after extended idling.

 

[KCLOST]

Re: 99 Yamaha OX66 250 Won't Accelerate After Idle

Fuel Bulb, mine clunked out on me just the other day....
Same symptoms, and after replacement all was normal...

 

[rodbolt]

Re: 99 Yamaha OX66 250 Won't Accelerate After Idle

KC
how will operating it in reverse affect a fuel bulb ?

 

[KCLOST]

Re: 99 Yamaha OX66 250 Won't Accelerate After Idle

I'm assuming he can't get on plane... WIth limited throttle in reverse, I thought it is just worth checking. May not be it at all...

 

[rodbolt]

Re: 99 Yamaha OX66 250 Won't Accelerate After Idle

a fuel primer going bad may restrict fuel, sounds like either its restricted or the low pressure pumps are failing to keep the VST full.
however I cannot see where running in reverse would affect fuel.
however it will move the shift cut out switch .
thats why I reccomend testing fuel rail pressure at the problem speed, not enough and it cant go.
the aftermarket bulbs seem to be problematic, the OEM yamaha stuff seems to last a few years.

 

[Control3391]

Re: 99 Yamaha OX66 250 Won't Accelerate After Idle

Thanks for the suggestions Rodbolt
I'll check the rail pressure ASAP. Because the motor is new to me, I plan on servicing the VST filter and at least cleaning the O2 sensor. The shift cutoff switch sounds possible due to the reverse operating normally and then clearing the problem. Now all I need to do is locate the switch! thanks I'll keep posting

 

[rodbolt]

Re: 99 Yamaha OX66 250 Won't Accelerate After Idle

the shift cut switch is located on the shift slide and needs periodic greaseing and inspections.,

 

[thanasi11]

i know this very old however I have exact same problem. will not accelarate, if i put it in reverse at high RPMS then back to forward it will accelerate . any ideas? Please help

 

[thanasi11]

rodbolt are you still out there?