Yamaha 90A 2s (2009) making knocking noise.

[fletcheriow]

I have a Yamaha 90hp 2s (specifically a 75CETO upgraded carbs to make it 90hp) however I've noticed a very obvious ticking or knocking sound when in idle, and when in gear but less audible.
It seems like quite a distinctive noise, I've tried looking up the issue, some have suggested piston slap, others spark issues, dirty or improperly fuelled carbs etc, but I've not quite managed to find a sound to match the issue from videos of others engines. I also checked the spark plugs currently in the engine and they are NKG BR8HS-10, the service manual says they should be B8HS-10 although this is contradicted if they have noise suppression? Haven't had an opportunity to remove the current plugs could it be its only running on two cylinders?

I've linked a video of the engine at idle

It also has an inversion kit on it designed to allow the engine to continue running after a capsize, no idea if anything to do with this would contribute to the issue?

Thanks in advance for any advice

[fletcheriow]

[fletcheriow]

https://youtube.com/shorts/0DeJeGIJaps

(Really having issues attaching the link)

[NC Pirate]

take a large screw driver and use it like a stethoscope, one end pressed to your ear and the other end on the motor and see where its coming from.
Probably wrist pin or rod bearing play (slapping). See if any piston has play in it

[robert graham]

A heavy stainless prop can rattle and knock on some motors. ....although my C90 Yamaha has a stainless prop and I haven't noticed anything very loud......Maybe remove the prop and run the motor tto see if it changes?

[fletcheriow]

Thankfully I had a stethoscope already otherwise I'd have been worried using a screwdriver with no flywheel cover haha. Wherever I placed the probe though it sounded the same, although this is likely my untrained ear, is there anywhere specifically I should have a listen? I mainly tried around the crank case. Also performed a compression test on all the cylinders and they all came out the same, would this rule out piston slap? As for the prop its only an aluminium one, and the noise is most prominent at idle when its barely moving, is it possible this could still cause it?