The lighthouse your are refering to is the Spindle Point Lighthouse and if that was to your left, you were on the westerly facing side of the cove. I remember rental cottages on Quimby road had a big boulder in front of those cabins. Pehaps that was it?
This listing is right near there for reference -
http://www.baysiderentalsnh.com/Unit/Details/72027
Maybe someone else here may remember more.
Good luck