It's marine-grade RG-8x. The antenna is at the top of the mast, 36 ft
above the cabin top.



My thought, in asking this questions, was replacing the current coax
with two of smaller diameter, since you said the current hole in the mast
was too small to add one. Commerically, we often use a RG-58 type coax
that has a white Teflon jacket, commonly referred to as Motorola White
Teflon coax. It is considerably smaller than RG-8X and I would hazzard to
say you might be able to pull a pair of them up, using the original RG-8X
as a pull line. You will need to obtain connectors with the proper size
ferrule for it as it is smaller than RG-58. Good Luck.

Ed K7AAT