Weak 1934 Nav Net 2 radar

My 1934 Nav Net 2 radar works but has a diminished signal strength. On auto setting, range is limited to 3 miles. On manual setting by stepping up the gain, I can get 10, 12 miles out of it but no where near 48 miles. Range switches are all on up to 48 miles. There is no experienced tech in my area (Mexico) so my local mechanic and I are self diagnosing. Where should I start? I

It depends on what you are expecting to see on the radar. Because of the curvature of the earth you wont normally pick up any boats beyond about 8 to 10 nm. Everything beyond that is mountains, skyscrapers, airplanes, birds or weather. If you know this radar and have seen diminished returns then you might be finding that your Magnetron is getting old and might need replacement. How many hours do you have on this magnetron?

Hello Johnny, I am only getting large freighters and large land masses at great distances when the radar is working normally. Now I am not getting those. I have an island 10 miles away from harbor which I can get but nothing beyond.
Transmit time on the magnetron is very low, perhaps 500 hours. High hours on the unit itself as boat has 5,000 hours and the unit is on at night as an anchor watch alarm.
Low transmit hours is why I am trying to eliminate other problems before buying a magnetron. Thanks for your help.

Bump, does anyone have a reply of how I should troubleshoot or should I replace my magnetron?

A magnetron is the most likely issue. Because of the cost and expertise involved it is best you contact your local distributor. Mexico does have support.

http://www.furuno.com/en/support/distributors/marine/