July 18 (Reuters) - Harley-Davidson Inc reported a 7.7 percent drop in quarterly profit and said full-year motorcycle shipments would decline about 6 percent to 8 percent, indicating slowing demand as its loyal baby boomer customer base ages.

The company said net income fell to $258.9 million, or $1.48 per share, in the second quarter ended June 25, from $280.4 million, or $1.55 per share, a year earlier.

Revenue from motorcycles and related products fell to $1.58 billion from $1.67 billion.

The company, which previously forecast "flat to down modestly" full-year shipments, said it expects to ship 241,000 to 246,000 motorcycles in 2017. (Reporting by Ankit Ajmera in Bengaluru; Editing by Sriraj Kalluvila)