One of the most frequently asked questions we get at http://www.springboardsandmore.com/ is "how tight should the diving board carriage bolts be when installing a diving board?"
The correct answer is 110 foot pounds of torque using an 18 inch handle torque wrench. You can purchase one of these at a local hardware store -- although they are a bit pricey ($50.00 - $75.00). You simply set the "torque" on the wrench to 110 foot pounds and tighten the board bolts until the wrench "clicks" or "slips" which tells you that the bolts are torqued to the correct setting.
It is important to "torque" the bolts to the correct setting so as not to over-tighten them as well as to insure that they are tight enough!
You should also try to torque the bolts that go into the deck (stand installation bolts) to 110 foot pounds as well -- although it is sometimes difficult to get the torque wrench onto some of these bolts.