Yamaha Outboards 3P Service Manual, Page 77Get this manual
ENGINE IS HARD TO START OR WILL NOT START
Is the compression of crankcase normall? Check the leakage of compression from the crankcase? YES
Check the following parts and replace as necessary: 1) Oil-seal 2) Crank casecrackeddistortion, scratches on mating surfaces
Is there any damage on the cylinder? YES IF THE TROUBLE HAS NOT BEEN FOUND, START THE ABOVE CHECKS ALL OVER AGAIN
Replace the crank cylinder assembly
NO Is the starter mounting position correct? YES Can the flywheel be turned by hand?
Correct it
Disassemble the recoil starter and check it(P5-13)