Split the engine & alternator in situ. End up with 2 smaller, light & far less unwieldy lumps instead of one big horrible lump.
In fact..if its just the engine that needs attention leave the frame & alternator in situ - just chock the alternator if it's a single brg/SAE disc coupling type
An A frame out of scaffold poles & small chainblock, guy the A frame & make sure the feet are on decent timbers to spread the load, Dont want a leg punching through the bottom! Make sure it cant swing while you are lifting it otherwise it might have the boat over.
Land it up onto timbers across the boat then slide off sideways. Make sure the boat is tied to the bank so it doesnt move outwards when you are halfway across.