I WAS WONDERING IN 1989 WHAT THE DIFF IS BE- TWEEN A 260HP AND A 270HPMAG I HAVE 260.IM ALSO LOOKING FOR MORE TOPEND I HAVE A 1989 20FOOT CENTURY CUDDYCABIN I TRIED A 15BY19P PROP AND WAS PUSHING 4300RPM.ANY HELP WOULD BE APP.