I just had the throttle control cable on my boat (18' BlueFin 90hp Johnson Seahorse)break. I removed the cable and measured it at just over 14" - so do I order a 14' cable or a 15'cable?Also, what is the normal idle RPMs for my Johnson, seems to be to slow during the warmer months (500 -700 rpm wihtout the idle arm full up, 1000 with the idel arm full up)?