I am going to be installing a 23' whip antenna for a new SSB radio
installation on my boat. My vessel is all-aluminum construction with a
center pilot house. How would you suggest mounting this antenna on this
vessel? I understand that it is important to keep the whip from coming
too close to any metal. This is an obvious problem, since this boat is
all aluminum. Any suggestions or references would be appreciated.

Well, I don't know if you are talking about something like a metal
Morad WH-23 or a fiberglass 23' Shakespeare or equivalent, but both need a
two piece mount. Probably some swivel bottom mount so it can be laid down at
times, and an upper support mount at least two feet up from the bottom.
Placing these two mounts as high as possible on the metal side of the pilot
house is fairly common. If you really want to gain all that length above the
pilot house, a fabricated aluminum tripod or sturdy welded post about three
feet high is cool.
The lead-in from the antenna to the tuner should be almost all outside
the aluminum pilothouse. Lots of boats (and ships) put the tuner outside the
pilothouse, near the antenna base to avoid any lead-in inside the
pilothouse. If you do the latter, very careful attention to sealing of the
coupler, and if you elect to vent it (Usually a plus), be sure the vent hole
is where the manufacturer recommends (at the very bottom, of course).
It would make suggestions a lot easier if you could post a picture or
drawing of your boat.
Tell us when you test so we can listen and report!
Old Chief Lynn