That was sort of an ersatz film culled from the “Dusty’s Trail” series, which was pretty obviously patterned after “Gilligan.” Apparently, “Gilligan” was doing gangbusters in rerun syndication in the early-70s, so to capitalize on that, “Dusty’s Trail” was produced and sold as a non-network, made-for-syndication series. Really low budget. Only lasted a single season, but I remember one of our local stations airing it on Saturday afternoons, around 1973.
I didn't get to see that show. Our locals didn't carry it but did Gilligan's. Island. First time I saw it was by renting the movie.