drive shaft

[widowmaker1]

ok so I got a broke drive shaft on my 2001 mercury-tracker 25 EL. Everything else in the foot appears to be fine,bearings turn easily and the gears look good,but a buddy told me that I should replace the whole lower unit cause something had to make the drive shaft break.Is this true? Should I replace the whole lower unit or just replace the drive shaft ? I have had this boat for 5 years and never had a problem,it runs great. Also,I was in deep water when it happened,didnt hit anything ,the shaft just broke.Thanks for any input.

[mercury2107]

I have seen shafts snap before and they always seem to snap below the water pump impeller. Drive shafts are made of two pieces that are friction welded together. Check the splines at the top of the shaft to see if they are twisted at all. If so........the propeller might have hit something or there might have been a piece in the gear housing break and bind. If not..the shaft could have had a weak spot......at that union

[widowmaker1]

no sign of twisting on the top splines-the shaft broke at the very bottom where the gear bolts to the shaft ,just above the bolt