Yamaha 90 2 stroke (2000) Lack of acceleration.

[mickmemate]

Hi. I hope someone can assist me. My Yamaha 90 2 stroke (year 2000) starts fist time every time. I went out on Saturday for a fish in absolutely fantastic weather and tried to leave the mooring and it will only accelerate to about 5 knots. It won't go over 2000 revs. When I got home I ran it again and it easily accelerated to over 2000 revs. So it seams only when its under load it has the problem. I have replaced the spark plugs and the fuel/water separator. I checked the plugs and all are firing. I have sprayed carb cleaner into the carbs. No Joy. Please help.

 

[99yam40]

there are some things that will limit RPM to about 2K,
Overheat and low oil level

 

[steelespike]

I would examine the mechanicals involved with throttle operation.Throttle cable?Carbs opening?Try squeezing the primer bulb.
Reving in neutral or on the muffs doesn't prove anything except that it runs.You could probably over rev on one cylinder on the muffs.