That bolt is actually a pulley. There's a service bulletin about this issue. I'm surprised Maytag/Whirlpool won't help you with this... Actually, I'm not surprised. Their service kind of sucks...
Anyway, you need to put some blue Loctite on the threads of the blower shaft threads(You can get blue Loctite from any automotive store). Then tighten the heck out of that pulley. To do this you need to hold the blower in place with one hand and use a wrench to tighten the pulley. Just tight enough with your own strength is good enough. The belt will go on. You need to put it on the pulley on the motor side first, then start it on the blower pulley. Now guide the belt around the pulley by turning the pulley to stretch it into place.
It sounds a bit confusing when you read this, but once you see what you have to do, it'll come to you. Let us know if you have questions.
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