2000 Mercury 175 EFI: had been running all day up to WOT without issue and engine shifting smoothly. I dropped my partner off at ramp and took off to give her one last final run before her winter nap. Hit 5600 RPM & 61 mph with a 23 pitch Trophy 4 (not Trophy plus) and suddenly heard loud bang and thought engine blew, but RPM stayed at/near same and engine did not die and idled fine.
A very loud metallic clang began coming from engine in gear but again RPM range was fine. I trimmed the outboard up and to see the prop and prop did spin slowly in gear for a moment and then stopped spinning after about 5 seconds when submerged. Motor did the exact same thing in reverse too, just spun just a few seconds and the stopped when submerged and then spun no further in either direction in gear.
Trolled to ramp and checked gear oil; there were some metal shavings on magnetic drain plug but not excessive, no water flowed out when plug was removed but lower unit oil level was low about 1/3 full and oil looked more aerated then having water intrusion and no additional metal shavings were drained out.
The motor seems to be running fine except it will not spin the prop and it's making one heck of a noise in gear. I thought if you grenaded your lower unit, your motor would die but it never did? I've never spun a hub before so I have no idea if that would clang loudly? The prop itself is fine it's not hitting anything. I didn't think to put it in gear and try to turn it or check for spun hub.
Questions, did I blow it up, break a drive shaft, or simply spin a hub (flo torque) if so would it make such a loud metallic clanging noise? Any other causes it may be? I put it away for winter after putting in new gear oil in and put it in the storage locker. It's some 200+ miles from my home and there it sits. If I go down in a couple of weeks, what & how should I check to determine the issues?
Thanks!