2005 Yamaha F150 knocking mystery

[Dhankinson]

Okay around 1000 hours on a pair of 2005 Yamaha f150's, have the latest balancers on them, compression good on all cylinders. Always maintained. So got about 25 miles from the inlet when strbd motor began knocking pulled the throttle back and it continued to knock at idle, shut it down. Brought it back and checked compression, started without lower unit to cancel that out, pulled balancer off no signs of wear oil clean, not dirty to say signs of a bearing. Suggestions please!!

Link to the video of the engine:
https://youtu.be/uMAReCEocek

 

[99yam40]

what did compression tell you?
plugs look OK?

knock sounds expensive.
large or small end of rod would be my guess or lost a skirt off piston

 

[Dhankinson]

150 +- 1 or 2 all 4, plugs looked good, removed valve covers all good there, digging in deeper tomorrow

 

[99yam40]

bore scope might help thru the plug holes
see if pistons/rods have slack