APBA was around forever. In the 70's they had two major classes of offshore racing. Open and Production. The Open class consisted of Open 1 and Open 2. Twin engine up to 1,000 cu in and single engine 500 cu inches.
Production was P for stock stuff, M for modified, meaning you could do a little balance and blueprint and carb changes and Sport for exotic stuff like speedmaster lower units and headers.....I think the lower classes had 750 cu in limit....(350 blocks)
The first Benihana started as the Around Long Island Marathon in 1959. Then Hennessey Cognac sponsored it from 1966, and finally it was known as the Benihana Grand Prix for the first time in 1975..... and won by none other than Mr Robert Saccenti. in a new MSV 44 foot boat called "La Tortuga".
The thing with OPC...Outboard Pleasure Craft class of APBA, was that a lot of guys came from that class...me, T2X, etc as we did marathon races and liked the long races and the navigation that came with offshore races.