First, raise the motor and put on support. Look for the lock mechanism, should be one or 2 pieces of metal with hooks made in. It should hook on a cross shaft assuming you don't have power tilt and trim. If that is the case it should have a spring that pulls and holds it in place until you trip a release to let it tilt up. If you have trim and tilt it shouldn't come up by hand at all. Just check the latch mechanism in the yard and you should be able to see what the problem is.