2001 225 v-max ox 66 knock sensor

Hello guys, my motor runs rough when it warms up at about 4200 rpms.When I unhook the knock sensor it runs good.I have fresh gas in it and the fuel system has been gone thru from one end to the other. Anyone experienced this?

Thanks,Eyecatcher

[boats.net]

We have had some knock sensor's do that. Try replacing it.