With out seeing it, one can only guess. A close up picture showing the grain would help. Is the wood stained red? Typical wood boat construction in the NE US was
white cedar planking over white oak frames/ribs with white oak or mahogany transom. Who built the boat? 1981 seems late for a mass produced boat.
My guess is mahogany which, though reddish color, is more brown. There are various species of mahogany with slight color variations. Western red cedar (I've worked with it) is possible but not desirable for a transom. Another contender is redwood, not desirable for a transom.