What do you consider to be an "OLD" boat? And just because you have an "OLD" boat does not mean you can not beat the fancy "new" boats either.
Most local racing is done on handicap, to hopefully level out the speed part of the game. Locally there is a late 60's, may be an ealry 70's Cal T2, the fellow has had since it was about 5 yrs old, Hard to beat him, no matter how new/fast you are.
Look up the local clubs that have boat races, join one, then doors are open all over the place.
She drives me boat,
I drives me dinghy!