It is best to pay a little extra and use marine grade tinned wire for two basic reasons. The tinning helps to limit corrosion. Unless you correctly crimp and seal the ends of the wire, water and moisture can intrude and cause the wire strands to corrode.
Second, although nominally the same, marine wire is a little larger than SAE (automotive wire). Marine wire also has finer strands making it more flexible and less resistant to work hardening from vibration and movement and subsequently breaking.
For mast wiring, I like to use duplex or triplex wires. These have 2 or 3 separate marine grade wires in a common jacket. The jacket provides some mechanical support, there are fewer wires slapping around in the mast, the wiring is more organized, and only one wire has to be fished up the mast instead of 2 or 3.
With boats there is a great temptation to use products from the automotive, RV, or household world. In some places this is perfectly acceptable, in other places these are a poor choice. When it comes to fuel, electricity, or holes beneath the waterline, the only good choices are marine grade products. Electricity, fuel burning outside the motor, and failed through hull fittings are some of the most common causes of boat disasters.