What is it

I would say that is some sort of repeater for a pirate radio station of some sort why it's on a boat frequencies that's confusing or and if it was on CB frequencies I would say its something that someone built to be a ar5hole and block out CB frequencies for some reason why I think this is because the two way switch that you siad about,that was definitely built for something special and not for normal CB use.

I think that's the best guess so far Martin. (Your 'a-hole' CB blocker suggestion.)

I remember the old pirate radio stations using simple VHF links so they could operate away from the transmitter but may have used other means.

But, I do recall some 'idiot', (I use that as the politest word I can muster), who built such a device to completely obliterate local CB operators, (and that tube as an antenna then makes sense). He lived on a boat at the local marina and was apparently 'sick' of CBers wiping out his TV reception so he constructed such a device to wipe them out. Don't think that would have helped his own TV reception, (again, idiot!), and was so powerful it was easily located by the authorities.
The 'boat' frequencies might make sense then as the reason they tracked down this boat marina guy was the spurious harmonics into VHF frequencies the damn setup was kicking out! (Wiping out Marina frequencies too no doubt.)

Cor, had forgot all about that, but it was back in 19-clickety-click 


Well done Martin, the more I think about it, the more right you are

Wish i had a counter to see the exact frequency it was on.
It was set on 13 but that don't make any difference as it's not on cb band.
I did try it on ch-1 and set my radio on  27.601 but nothing when i transmitted.
The burner was a jaguar 100w but a big thing for it's power.(working so ebay job)..
Whoever made it spent some time doing it as it took me a good hour to strip it all little bolts everywhere.
It came from Great Yarmouth.
We never know the original might see it on here and let us know what it was built for.

The reason the bit about the CB radio blocker came to me was because I knew someone who built something like that but on a very very small scale to annoy a idiot we had around our way the one this guy made only block out about 100yrds radius  ,he made it put it in a box it ran off a battery if I remember correctly a PP4 a 3 inch square battery and put it in the idiots front garden in a bush and he couldn't work out why he couldn't get out lol

Maybe the copper reflector and strange tube are for getting a suntan while chatting on the cb?

Ha! Like it Ernest! Top up that 'holiday' tan whilst operating.

Well the tuner serviced new bulb well LED fitted and working spot on.
So i got what i wanted plus some junk for the bay lol.