You should rip all the outside wood off so you do not have to so much
work maintaining it. Replace your hand holds and trim with Steel!

That said, I have solid mahogany spreaders, I sand and varnish them
about every other year. A fun summer day project. If I had teak deck Id
let em go gray. I used Cetol last time I did my spreaders and the
celtol seems to hold up longer than varnish, yet varnish looks way
better. 8-10 coats of varnish is the way to go, wet sanding with 600
grit Norton sandpaper between every coat. My whole interior is
phillipino & hondouran mahogany with 8 hand sanded coats of Epifanes
Varnish, It took that many coats because I selected mahogany mith
intense mudulley rays that are very porious and sucked in the varnish.

Joe