Tapping doesn't reveal anything. For it to sound hollow, takes decades after the rot starts. Take a test drill and check the shavings. FLIR camera will help. Also, weigh the boat and compare to spec.
You measure from the gunwales to the Static Water Line, you measure from the gunwales to the top of the riser. The difference should be greater than 13 when your boat was new ( now 14" )
Your past the camera inspection stage. That was within 20 hours of water entering the engine
Your at tear down phase.
The heat exchanger should have kept water from the motor unless the hull is water logged and it ingested water because the SWL to riser dimension is less than 13"
I would make sure it's past the break in period. I would also check with your dealer
However with that load, you may have to loose a blade or drop down in pitch
the B230 engine in the AQ145 is a modified automotive variation of the motors in the Volvo 2 series. the AQ125 may work (would have to verify the PDS), however you will be down on power.
what is broken on the motor? it may be easier to fix than to replace.
