We’ve been wrestling with the SONAR decision for the last couple of weeks. Based on our sea trials with Furuno, and the comments by John Harries (see previous articles) we came to the decision that some sort of a system makes sense for us.

We arrived at this point for several reasons: First, with the new boat we are exploring a lot of cold weather anchorages for which good charts do not exist. (The fact that these charts are not available is part of what intrigues us!) The water is murky and hard to read, so a forward-looking SONAR has high value in this environment. Next, the fact that SONAR should work really well in the tropics, with deep lagoons and vertical coral walls/heads, means we have more options if eyeball navigation is not possible. The cost of any of these systems is substantial by the time you figure a haul-out (which we do not need right now), hardware, and wiring. But then the cost of an unexpected haul-out for damage to props or stabilizer fins is high too, and would mess with our cruising plans.

We’ve decided to go with the Furuno CH270. This is a very high-quality unit, which gives us maximum flexibility in how it is used. We think that for our needs, having the ability to scan horizontally and vertically – in narrow and wide angles – makes good sense. The CH270 will also operate at much longer range than is the case with the simpler forward-only-looking SONARs.

One aspect of the CH270 which is particularly appealing is the audio output. We can connect a speaker to the set, and then hear what is going on ahead of us based on the return signals. We’ve been told that a solid target will give off a noticeable change in pitch and volume. In theory, this should allow us to focus on other nav aids, and then investigate the SONAR screen only when required. If this works as expected, it will allow the two of us a great deal more latitude in how we divide our navigation duties.

Our second choice was Echo Pilot. We think this would make an excellent approach as well. It does not require the 6-inch (150mm) hole in the bottom we will be adding for the CH270, and is about a quarter the cost. Space requirements for the transducer and electronics are also significantly less.

The decision to spend the extra money on the high-end Furuno SONAR was not arrived at easily. However, in the end, we felt that the investment was justified by the extra margin of security this unit should – in theory at least – give us. Assuming, of course, we learn how to use it properly, and it works as we hope.

We’ll know soon enough.