My Dad always kept a pair of pantyhose in the old salt boat for this. Cut one leg off, tie it around the pulley's and start her up. As the thing turns, the pantyhose twist and tighten until they have enough friction to pull water pump and alternator. Don't ask me how he figured that out, but it works, and last's an incredibly long time. For years I kept a pair in my truck and boat, until I got smart enought to buy a spare belt!