Don't know about 170's
Most suppliers (West Marine) will offer a selection chart. The selection for your boat will be based on the length and gross weight of your boat. 8# is right for a 17 foot, but buy a 12#. The price will be worth the piece of mind. For sand bottom, soft or hard, a fluke anchor would be the best. You could use a folding grapple anchor. It would be easier to store onboard and have good holding capability. Ground tackle is a very important piece of equipment even for a trailer boat.