Having a problem and hope somebody can give me an idea:  I got this engine new as a kid back in 57/58.  The original motor in it -- fried.  I finally found one to replace it on line.  I had to attach the original worm gear to the new motor.  Anyway to make a long story short, it runs great--IN REVERSE.  It will go about 3 inches forward and then catch. 

The worm gear does not hit the frame and I also put one small metal shim washer under the motor where it screws to the frame on each side.  Without the shims, it wouldn't move at all. 

Anybody got any ideas??