Had the mast down, so made some measurements of the round mast on my 1984 F25:
Wall thickness @ base: 5/16"
Length: 36’ 2-3/4" overall
Base to deck penetration: 47-3/4"
Deck penetration to top: 32’ 3-1/2"
Circumference -
@ Top: 12-3/8"
Top - 10’: 15-3/4"
Top - 20’: 18-1/8"
Top - 30’: 20-7/8" (*)
Bottom: 21-0/0"
- 6" below gooseneck