Joel,
You need to connect yellow from your Lowrance cable to pin 2, and the shield (the uncovered wires) to pin 9.
I don't think there is any standard to the wire colours in serial cables - or at least, if there are standards there are more than one - so you either need to use a multi-meter to determine which wires are running to which pin in your DB9 plug, or get hold of a DB9 male connector and use that (cheap, but you need a speciality store).

The pin layout:



Matt