This is a vintage, 20th century, dated 1947, original oil on board painting by an American self-taught Outsider artist, Joyce Van Tassel (b. 1921) depicting a speedboat racing through water with a double rainbow in the background. This painting was painted before she married and was known as Joyce Van Tassel Page in 1957. The oeuvre, or most recognizable and developed style of her work came about post 1947 and there is a marked difference between this work and what she 'is known for', per se. Being outside of that norm, the work is not as sought after as her later pieces.
The estimate is based on actual recent past recorded auction sales of comparables. Retail 'asking prices' can be higher and vary.