www.battlewagonmounts.com has links to every manufacturer's current and retired owners manuals. Click on the radar mounts page and then the manufacturer. Quick and easy.............
I'm all for saving a buck in fact my wife often refers to me as cheap. That said this is one item I would not buy used if it is more than one generation old because if there is anything wrong with it there is no parts or repair support from the manufacturer.
Go to furunousa.com and search for a 1942 MK2 radar. Have one that just came off a boat and works perfectly. And...the magnetron is new. Send me an email if interested.
Furuno has the best customer service I have ever delt with. If it's Furuno they are happy to help regardless of age or where you got it. Magnatrons may be life limited but most people never even turn their units on the majority of the time.