Thread: Tm260 or Tm185m

Of the two mentioned the TM260 is the one I would go for in 400m depths. The 185 is a shallow water unit, fixed transducer beam angle of 25deg which equates to a footprint of 100m at 400m - not very precise. On the other hand, the wider beam angle in shallow water is a lot more useful and the 260's 200Khz beam angle of 6deg is a bit like writing with a pencil vs spraying with a hose. Frequency isn't a problem as you are well within the envelope for 200Khz (or higher) - I was getting bottom lock in 1100m with 200Khz and a SS270W transducer in a thru-hull application. That's at the extreme end of what you can get out of a 1Kw rated transducer and that was used as a sales tool as well as a fishing tool but it does show what the things can achieve when correctly installed and set up. I'll add the edit there that the 270w has dual 25deg beams and the level of precision was the only thing that annoyed me about it in use - it was bloody hard to position the boat over the top of deeper structure although I did get better over time by looking at the thickness of the traceline and estimating how far off I was and checking with a cross-pass before setting up.

Never used the 256, although it seems to be narrow beam on both frequencies - I'd go for wide on 50Khz and narrow on 200 if selecting one nowadays???