The torque spec is listed in the service manual (16.6-18.1 FT/LBS).
You can end up with leaks here if sealant wasn't applied to the flange faces around the crankshaft main bolts ,or if the flanges aren't pulled tightly together . You can take the bolt out , clean it with solvent , apply a non-hardening sealant to the underside of the head and both sides of the washer , and reinstall . This will probably seal the leak . If the bottom hasn't been apart , the bolt may have just loosened . Simply re-tightening may stop the leak. I assume your talking about a 750 listed in your avatar .
Mike