Mitch, is this a special bolt with a flange sticking out slightly?
If so, you need to use loctite 272 (red high strength) apply to the threads of the bolt and also on the threads in crank snout and also between the pulley and balancer. Have a small amount of oil applied to the flange of the bolt to aid in torquing do not let the oil contaminate the loctite. Bolt torque 311 ft. Lbs. This is right from toyota.

This isn't a mercruiser, you will damage the balancer and pulley after they come loose and they are close to 1500$

Also if the balancer was off you need to put sealant around the inside and where the keyway is or it will seep.