The Boston Marathon, a late entry into...

The Boston Marathon, a late entry into the big-money era of road racing, has reached a rich sponsorship agreement that will extend through the year 2008.

The 20-year deal between John Hancock Financial Services and the Boston Athletic Assn., announced Tuesday, replaces a 10-year, $10-million arrangement that began with the 1986 race, its first sponsorship.

Under the new agreement, which starts with Monday’s race, Hancock will provide an average of $1.3 million per year in funds and services through 2003. It includes a five-year option through 2008.

Money will be used to reimburse the state and the eight cities and towns along the course. Some of the funds also could be added to the cash awards at future Boston Marathons.