OX66 rpm issues..... maybe?

[newberryfam]

I have a 98' OX66 250 that I recently purchased. I am not sure if it is anything or not, nut I wanted to ask the yamaha guru's here and see if I can get some advise. At idle the motor runs great, and at high RPM the motor runs great as well. It is when I am in a middle RPM that does not seem right. The motor ocilates back and fourth between a higher rpm and a lower rpm. Buut if I push the throttle up a little, it will increase rpm with no problem or if I lower the rpm a little it will decrease and stay constant with no problem. The guy that I got the boat from said that with it being a V6, at lower rpm, the computer will shut off two cylindars so it helps to save gas. At higher rpm, the computer will fire all 6. He said that at the medium rpm the computer can't decide which to run so it goes back and fourth since it is trying to use the correct setting. It this true or do I have a problem with something?

 

[Tucker99]

Re: OX66 rpm issues..... maybe?

Lots of things to check, begining with fuel system and ending with O2 sensor.

 

[lawcki]

Re: OX66 rpm issues..... maybe?

I have the same problem with my 2000 250 HP OX66. Did you found the problem on your engine ?

 

[airwo.lf]

Re: OX66 rpm issues..... maybe?

My 1998 OX66 225 does the same thing

idles perfect, and runs great above 2800 rpms seems to run rough at low speeds ( low rpms )