cleaning with vinegar?

Any fiberglass/gelcoat gurus out there that can shine some light on this? My friend uses 100% vinegar to clean his boat. He said the dealer (crownline/sanger) said this is best way to keep it looking new. His method is simple: using a sponge he wipes down the boat with vinegar then uses a towel to wipe the excess vinegar—he does not rinse the boat. It definitely works especially for the tough water spots. I am hesitant to use this method until I know for sure it will not ruin my boat’s gelcoat?