1971 Mercury 7.5hp,, sputtered and then something broke, motor won't turn over now

[Ruthless3190]

After launching my boat, I started my 1971 Mercury 7.5hp motor,, sounded alittle rough but was running the same as it did last week on the water. I got about 350yards across the lake, then the motor started to sputter and I heard something that sounded like a part breaking or ceasing,, then the motor shut down and will not turn over again. I pulled the rip cord to try and get it re-started, sounds like something is grinding or broken,, plus my rip cord is very slow to recoil. I had the spark plugs and impeller changed last year. I noticed a slight oil leak around the gasket behind the propeller last night before I loaded my boat.

Does anyone have any suggestions or comments????, I will be taking the motor into a marine mechanic in the next couple weeks, so anything that I could tell them would be greatly appreciated