Very loud "thunk" while underway...

[nola mike]

'03 25hp 2 stroke merc (no s/n handy, sorry). Cruising today at 3/4 throttle, no problems, and I hear a very loud "thunk" sound, and motor starts to rev. I immediately pulled off the throttle and went to neutral. Engine sounded fine. Shifted into fwd/neutral/fwd. No problems. Went slow for a bit, then opened it up and all seemed well. Got home, pulled drain plug, looked good, no metal. So, what happened? Sounded like the motor slipped out of gear, but that shouldn't happen if my gears are good, right? Anything I should check? No slipping after that one instance, manually turning the prop in gear turned the engine, doesn't seem spun. It sounded like a "about to self-disassemble" sound, which I didn't appreciate.

 

[Scott Danforth]

Hit a floater?

 

[roscoe]

Hit a floater?

A Baby Ruth ???

 

[w2much]

If it was not the baby ruth or other object I would say to check your shift rod and cables for proper adjustment. I have had the same unkwown clunk which turned out to be a bad lower unit probably caused by me when changing out the impeller and not checking my shift rod adjustment upon reassembly. Also check your hull for skid marks from a baby ruth.

 

[QBhoy]

Check the trim pin bushing hasn’t moved, just in case. If it has