Garmin 340C Fish Finder 50khz not working

[Grant Brown]

We bought the 340C over the winter and took it out for the first time this year. After playing with this unit for the day no matter what I did I can not get it to read the bottom when on plane. (Salt Water) Even in 20' of water. Once we stop it does pick up the bottom but we did not try over 300'. One thing I noticed is the 50K small beam does not pick up well at all even when trolling. We played with different angles of the transducer. Which is the most power for reading. single 200 or 50? This is on an 20' Aluminum boat and have it wired to a 2nd battery not on the main motor. It is mounted to the port side about 5-6" from the edge as the inboard leg and trim tabs take up most of the area.

With the boat trolling or stopped I adjusted the angle of the transducer to various angles and could never get the 50K to register properly. At 150 feet of water the 200K read perfectly but the 50K struggled. I made sure it was pointing straight down. It seems like the 50K part of the transducer is not working or has a problem. Have you seen this before where one of the frequencies are faulty?

On my small 14' Aluminum I use a Eagle Tri-finder and before I go on plane I turn off the side beams and use the 20 degree cone.

I am thinking of buying another transducer to rule out that as the problem with the 340C.

Grant

 

[Bondo]

Re: Garmin 340C Fish Finder 50khz not working

After playing with this unit for the day no matter what I did I can not get it to read the bottom when on plane. (Salt Water) Even in 20' of water. Once we stop it does pick up the bottom but we did not try over 300'.

Ayuh,... It sounds like it's loosing contact with the water, when on plane...

 

[Marsman]

Re: Garmin 340C Fish Finder 50khz not working

Hi,

After working with Grant on this I came across something very interesting. In the manual on page 2 it says that the 50kHz shows less details but penetrates deeper. But I came across on E Bay when looking at possible buying a new transducer that the 200kHz shows less detail and penetrates deeper. I sent an email to Garmin and confirmed that the 200kHz is the smaller cone. This now helps in the testing and learning to get it to read when on plane.

Here is what I found on eBay. This tells me to run it at 200kHz and look for the angle of the transducer more closely and possible cavitation.

Beam-width of 15 degrees at 200 kHz, 45 degrees at 50 kHz.

Cheers, Rob

 

[dingbat]

Re: Garmin 340C Fish Finder 50khz not working

I am thinking of buying another transducer to rule out that as the problem with the 340C.

Grant

The transducer uses the same crystal to produce both frequencies. If you're having what you think are frequency problems the issue most likely resides in the head unit.