I broke a belt when my motor had 50 hours on it. I had just checked it out for slack and it was good and tight with no signs of wear or anything. I hit something at WOT and that was all she wrote.
It was a fluke, since then I've hit many more things much harder with no issues. It does sound bad sometimes but its not an issue and I have put over 300 more hours on it.
Slipping has never been a problem for me. I did have to shim the motor after about 150-200 hours to pull some slack out of the belt but it never slipped at anytime.
You can change the belt in the field but not in 6' of water. If you are in an area with a hard bottom it would be a snap, if not I would try to get it on the bank to work on it. You will have to pull the lower unit but thats not really hard at all. The hard part is getting the belt back over the bottom pulley, but once you learn the trick to that its not bad at all. This is very easy to do in the driveway
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