Re: Tohatsu M8B
To add to what the others have said. If you didn't mix 50;1, your in deep Do-do and IMHO, the repair may cost more than the motor s worth.
Assuming you fed it correctly, then it could be something much simpler and cheaper to resolve.
First, when you attempt to pull start, is the motor in neutral and can you turn the prop freely by hand? If "yes", your problem is up top and quite likely in the cylinder or crank . (a compression check would be the next step.)
If "no", then your problem may be in the lower unit and/or the motor is out of adjustment for gear engagement. The next step here would be to drop teh leg as previously suggested.