50 hp merc lower unit

[bretster36]

I have a 1972 Mercury 500 50 hp was wondering what years the lower unit will interchange. I have a 1970 for parts, looks the same. Also what seals do I need to order and replace in lower unit as it leaks all the oil out? and tools?

[boats.net]

There was a lot of changes in gearcases and not sure which ones would work, would need to look up parts for the serial number of motor that the gearcase came off of to make sure get right seals.