I don't know if this is technical, but I am wondering if the 4-blade fan I got that has the different bolt pattern and will not bolt on to replace the 3-blade fan that is on motor? Would work fine if I drill out the holes and grind between the creating a slot.  Would this cause an issue with water pump life span? The center holes are the same size and both fit snug on shaft.  My concern is would fan be out of balance maybe to point of taking out water pump?  There does not appear to be any balance weights on the fan.  As it rests on the center shaft and bolts then secure it.  Am I just over thing this? Sorry if this is a dumb question. .