Have a problem here thats been a trend in my boat shop for the last 2 weeks.
I've been discovering motors that make an extremely high pitched whining noise that seems to be coming from the lower unit at WOT. It's been driving me mad. Our main line of motors are 55 HP Johnson outboards, Military model. Our props are encased with a stator cone.

I have checked the mounts of the stator cone to the impeller. Seems like they have been rubbing against each other quite hard. Shaved down quite a bit. And the rubber bumper on the impeller which mounts on to the thrust washer on the prop was worn down significantly, so I changed out the stator cone and impeller. Started the motor up and ran WOT. Still the same issue. So I gutted the gearcase inspecting each component. Gears, dog clutch, pinon. All checked out fine. Anyone have any input on this issue? Maybe something I may have missed? I appreciate any help on this. Thank you.