There is no "oil pan" per-say, the engine is solid cast metal in 2 halves that have the crankshaft sandwiched between them held together by large "stretch" bolts accessed thru aluminum plugs in the bottom half (only visible and accessible when the engine is upside down on a work table or stand).
You might can take the PTO assembly off the back of the engine (still in the hull) and find that bendix gear, it's most likely in the bottom of the PTO housing as that's where the starter gear is located on the crank. But if you don't find it in there, then you'd have to pull the engine case out of the hull and split it open (essentially dismanteling the engine... you'd need new gaskets including new head gasket, and all new stretch bolts along with a service manual for the torque settings and torque order and a good adjustable torque wrench). This is no fun at all... .sorry! :-(
ps. The stretch bolts all have funny looking rings on them under the bolt head down to the actual threads, they "stretch" to the correct length the 1st time the engine heats up to normal operating temps... you should not re-use them, as they'll "stretch" again when the engine again heats up and may break as the steel can only be stretched so much before it fractures so most people throw them away and go back with brand new virgin stretch bolts. To take the PTO assembly off you don't encounter any of these stretch bolts, but take the engine head off or case apart and you'll need new crankshaft stretch bolts as well as new head stretch bolts (as well as a new head gasket, never re-use that part either!).
- Michael