Changed my water pump in a hotel parking lot last week.
There are 3 holes not threaded, the 3rd is the tensioner, but the bolts are grade 8.8 and the water pump is aluminum, before the water pump is in take the bolt and rachet and slowly screw it in, the 8.8 hardened bolts will thread in the aluminuim, thread 3/4 in take the bolt out and you will see the threads on the bolt will be perfect and threads in the water pump housing, then put the rest of the bolts in and last 3 that are 3/4 threaded in will finish threading and help lock in the bolt.