SONAR for Shallow Water

[jaymoussy]

My primary boating is mostly slow speed pleasure cruising in an inner bay, and I often find myself in shallow water, with potential for [the outboard engine skeg to be] dragging. What kind of [SONAR or other] electronics would give me the best depth reading?

I have no legacy electronics at all on my Montauk 170.

[Jefecinco]

If depth of the water behind your boat is your only concern you don't need to spend the money for a fish finder. I would look for an inexpensive depth finder and transducer combination if you can find one. A black and white or gray scale machine should be fine.

[Dutchman]

I have used Hawkeye and Lowrance depth finders on several of my boats and both can be had for less than $100. These are depth sounders and not fish-finders. Better let Santa know. Mount transducer at bottom transom.

[Acseatsri]

I would opt for a chart plotter with a detailed chart card over a depth finder. The downward-looking transducer only shows the water depth under the stern of the boat--too late to avoid hitting bottom. Better off with the [chart plotter]. Set up the [electronic chart display options in some unspecified manner so they] highlight the shallows and just avoid them.

[porthole]

My own inboard boats and every inboard I ran had a simple digital depth gauge. Always on, no adjustments other then setting the keel offset. We always used a through hull transducer on the bigger boats. If my boating was what you described, I would add a simple gauge, thru hull or transom mount.

[jimh]

I don't know what the water clarity is where you are operating your boat, but in the Great Lakes, where I am boating, you do not need a depth sounder to let you know you are in water that is less than 20-feet deep. You just look over the side and see the bottom.

I prefer a SONAR with a display showing the depth history in preference to just a digital reading of depth. You can usually see a trend in the depth. If I see the bottom is coming up rapidly on my SONAR display, it gives some warning time to the helmsman.

Since you have no electronics at all on the boat now, I recommend getting a combination device that will have

--a GNSS receiver
--a SONAR
--a multi-function display
--embedded digital chart cartography with good detail for your boating area
--a chart plotter
--a navigation computer
--a fuel manager
--a trip log
--and divers other systems

instead of just getting a depth finder.

A multi-function display can be configured to show multiple panels or windows simultaneously, or to show many full-page windows of different information, one at a time, or to show overlays of important information over many of those windows. In general, these modern small boat electronic devices are amazing and are excellent values. Their cost is modest and they deliver an amazing amount of information.

Choosing what device to buy is mostly a matter of your budget. As depth finders, they all work about equally well. If your budget is limited, you can find an obsolete product being promoted at close-out prices that will be a good buy. If your budget is unlimited, then your choices are similarly unlimited. Without some notion of budget, it is difficult to know what to recommend to solve the problem.

The time between new product introductions in the marine electronics market of today is about 90-days. Many new products are introduced or become available around February each year, as this corresponds with major boat shows and fitting out for spring. At the moment, if I were going to buy a new multi-function device for a small boat, I would give first consideration to the SIMRAD GO7 XSE. It has not yet hit the market, but there is some preliminary information available.

As for a transducer, you will most likely use a transom mounted transducer. A Boston Whaler boat like a 170 MONTAUK is extremely unsuited for a through-hull transducer because of the double bottom hull construction. Generally through-hull transducers are only used on larger Boston Whaler boats in which the hull has been designed and fabricated with a special area, called a putty box, through which one can drill a large diameter hole and install a through-hull transducer. For a 170 MONTAUK you will be much better served with a transom mounted transducer. It will be far less expensive, require far less modification of your hull (which might void your hull warranty), and will work just fine.

[Jefecinco]

If your boating area is in charted waters you can save the cost of an expensive electronic device and instead use a chart to provide depth information for where you are. For several years in the era before electronic chart plotters I used a chart and a depth sounder to avoid going aground. A simple depth sounder is a useful navigation tool when using a chart. It can often help determine your position to compare the charted depth with your actual depth in conjunction with charted landmarks or navigation markers.

Despite knowing where I was I dinged my propeller a couple of times when transiting marked shallow areas.

If your boating is in uncharted waters a chart plotter is a very useful, almost essential, navigation tool and safety device.

[Acseatsri]

Re water clarity: in Long Island Sound if you can see bottom, especially during the summer, chances are you're dredging your own channel. In the spring, before most of the boats are in the water, you can probably see to 5-feet or 6-feet deep.

[jaymoussy]

Thanks for the SIMRAD suggestion.

It would work nicely, of course, but quite a few features would be beyond my plain recreational needs. OTOH, I need something, and I may grow to like some extras .

It looks like I would need to add maps to the SIMRAD offering, perhaps Navionics, at extra cost.

Then the screen size comes into play, 7-inch versus 5 inch on my virgin Montauk console. Maybe the 5-inch running in split-screen mode [chart/depth] is fine for my needs. The waterway is uncomplicated, and I am not chasing fish, really.