Panther - High-Speed. 15 ft. Inboard Runabout - By William D. Jackson. Here, veritably, is a projectile for water borne space travel, an inboard Speedster with super clean and efficient running lines. With any present day automobile engine ('54 or later), or even with a "souped” '46 to '49 Ford or Mercury, speeds of 75 mph are possible with no sacrifice of stability. On the contrary, because of the employment of advanced methods of strut, rudder, rearward motor installation, vibration is kept to a minimum and hands off steering is possible.