I noticed last year that my throttle cable was slipping and seemed really loose. I have decided to change it, and was wondering how exactly I would go about measuring it to ensure I purchase the right length. 

There is a couple of different ways you can go about doing so.

 

First is to take it out completely and maeasure it, this usually ends up with the best result or most accurate measurement for me,  or the second is to take a tape measurer and measure from the throttle lever to the stern, then from the gunnal at the stern to the entry of the engine case or where it makes the bend to turn into the case, then from the bend to the engine's throttle lever and add all of those measurements together to get your total length.

 

Most cables come in different lengths of either inches or feet, depending on the manufacturer, if you use the second method of measurement, make sure to add about a foot to the measurement, you loose a few inches when you are measureing in straight lines, another factor to keep in mind is to look at your anchoring location on the throttle control lever, some cables are screw locked and some have metal locating pins, most cables at the throttle lever located on the engine usually have a screw lock depending on the make and model, but the other end may very well be completely different.

 

One other note, if you take the cable out completely, make sure you have a small rope or I like to use mechanics wire, and attatch it to the throttle control lever end, as you SLOWLY remove the throttle cable the cable routing will be much easier for installation, pulling the mechanics wire back toward the the throttle control lever allows the new cable to come back the same path as the old one used.