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Author Topic:   Depth Sounder selection
Riverwhaler posted 06-06-2007 08:11 AM ET (US)   Profile for Riverwhaler   Send Email to Riverwhaler  
I currently have a Humminbird fish finder for a sounder on my Nantucket. It is not entirely successful, at certain speeds screen doesn't read any bottom. I have tried changing mount on transom, even tilting it differently. It still doesn't work reliably. The transponder size is small on the Humminbird. Maybe the bubbles and turbulence from the engine are the cause. This unit comes from Walmart for $90 so I shouldn't expect much. Does a better unit (a Garmin) work more reliably?
jimh posted 06-06-2007 09:16 AM ET (US)     Profile for jimh  Send Email to jimh     
My experience is when the SONAR transducer is installed in a good location, you usually can maintain a bottom echo and have depth readings while the boat is on plane. The biggest influence is the transducer and its location. However, it is also reasonable to infer that a more expensive SONAR will have more power. Using more power will produce a stronger echo signal, and this will also influence the performance while at higher speeds. A more expensive unit may also have a more sensitive receiver, as well as better automatic gain controls. However, on a less expensive unit there may be some manually adjustable controls which will improve the performance. Check to see if you can increase the receiver gain.

In my installation I can just see the bottom echo when on plane and going more than 25-MPH. I cannot see any detail or obtain echoes from any targets othe

Regarding bubbles and turbulence from the engine:

The transducer should be upstream of the engine, so it is hard to imagine how a bubble could travel upstream against the flow of water at, say, 25-MPH to reach the transducer. As long as the transducer is about 12- to 15-inches outboard from the motor there should not be a problem with the propeller wash affecting the SONAR.

I have found that changes in the vertical position (or the depth of immersion of the transducer) as small as 1/4-inch have an effect on performance.

jimh posted 06-06-2007 09:25 AM ET (US)     Profile for jimh  Send Email to jimh     
Re "better unit": Humminbird makes very high-end SONAR devices, much more sophiticated than the $90 model you have now. They have been making SONAR devices much longer than GARMIN, so I would not automatically conclude that a Garmin unit is inherently better than a Humminbird.
bluewaterpirate posted 06-06-2007 10:32 AM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Triva question ......

Who employed the owner of Garmin prior to him starting the company?


Dick E posted 06-06-2007 12:47 PM ET (US)     Profile for Dick E  Send Email to Dick E     
Gary Gurrell and Min Kao founded Garmin
Gary first three letters”Gar and Min first name “Min” spell Garmin
Gary worked for King Radio for the most part, but did work for Lowrance Electronics
Also David Cassidy of Partrdige fame help founded the company
bluewaterpirate posted 06-06-2007 01:44 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
You win first prize .....
tombro posted 06-06-2007 03:05 PM ET (US)     Profile for tombro  Send Email to tombro     
Very interesting, thanks.
K Albus posted 06-06-2007 03:44 PM ET (US)     Profile for K Albus  Send Email to K Albus     
A more powerful transducer is not necessarily always a good thing. I do most of my boating in the Great Lakes and in various inland lakes in Michigan. I am often in very shallow water, but sometimes also in very deep water. I have found that a sonar system with a more powerful transducer oftentimes will not work properly in very shallow water. I am no engineer, but it seems that at very shallow depths the output from the transducer overwhelms the system and the bottom reading is lost. When I am in shallow water, I usually switch my sounder to the manual setting with the gain reduced as far as possible. Even then, I will lose the bottom reading in anything less than about 2.5 to 3 feet.
pglein posted 06-06-2007 04:15 PM ET (US)     Profile for pglein  Send Email to pglein     
I would think that when the water is only 2.5-3' deep it wouldn't really matter anymore if it didn't show up on the depth sounder. At that point you're going to have the engine raised and be poling back to deeper water. Or stuck waiting for the tide to come back in.
K Albus posted 06-06-2007 04:31 PM ET (US)     Profile for K Albus  Send Email to K Albus     
We don't have any tides to contend with in the Great Lakes. Also, poling would be impractical in many cases. For instance, on Lake St. Clair there are dozens of square miles where the water depth is only 2 to 3 feet. See .

Having the sonar lose the bottom in an area that you know is shallow is not the problem. The problem arises when you are boating in an unfamiliar area, especially one with murky water, and you can't tell how deep the water is. My boat will run fine, with the motor down, in 3 feet of water. With the motor raised, I can handle 2 feet of water. But if the sonar is not providing a reading, and the water is murky, there's no way to tell if there are submerged rocks, logs, or other debris. For larger lakes, you can use a chart to locate obstructions or figure out the depth. For most inland lakes, however, detailed nautical charts are not available.

K Albus posted 06-06-2007 04:44 PM ET (US)     Profile for K Albus  Send Email to K Albus     
A couple more points:

1. In order to get the depth readings in shallow water, I have to switch my sonar unit to the manual setting with the gain fully reduced. At this setting, however, the sonar will not provide a depth reading while on plane. It also does not provide good readings in deep water. This means that when moving from deep water to shallow water, or vice-versa, I have to goof around with the sonar unit when I should be paying full attention to navigating.

2. It is somewhat common to cruise over the shallow areas of Lake St. Clair on plane. The shallow areas are very large, and they take a long time to traverse at idle speed with the motor raised. The bottom is essentially all sand, so hitting the bottom is not a big deal. (Nevertheless, nobody likes to hit bottom.) With my sonar set to the manual setting at fully reduced gain, I cannot get a bottom reading while on plane. In the shallow areas of Lake St. Clair, a bottom reading is a very helpful piece of navigation information, especially if you are in 2 to 3 feet of water.

3. My primary point in my previous post was that if the original poster boats primarily in shallow water, a more powerful transducer may not be the answer to his problem.

Riverwhaler posted 06-07-2007 08:48 AM ET (US)     Profile for Riverwhaler  Send Email to Riverwhaler     
Ok you have convinced me to try adjusting the transducer again. It is flush with the bottom of the hull but the tilt gets out of adjustment. The transducer is smaller than the Garmin, don't know if that makes a difference.
The response from this site always amazes me.
handn posted 06-07-2007 11:52 AM ET (US)     Profile for handn  Send Email to handn     
Higher end sonars have dual frequencies. High frequency is for shallower waters and better discrimination of features and fish on the bottom at shallower depth. High frequency also works better at planing speeds.
Low frequency is for deeper water and will give accurate depth readings at deep depths.
Most sonars have range and gain settings and the minimum of each is desirable for shallow water.
I doubt that any sonar will help to avoid bottom hazards at 2-3 feet.
Casco Bay Outrage posted 06-07-2007 12:29 PM ET (US)     Profile for Casco Bay Outrage  Send Email to Casco Bay Outrage     
Allan -

In many threads on mounting transducers (sonar/depth etc), I recall that photos help the pro's (not me) see if the position is correct.

Can you post a photo and provide a link?

i had a cheap Hummingbird on my classic Montauk and once I installed the transducer correctly, it worked well. I could maintain readings up to 35+ mph.



Ranjr13 posted 06-08-2007 05:53 PM ET (US)     Profile for Ranjr13  Send Email to Ranjr13     
I have a "cheap" Hummingbird ($89.00) on my 11' Whaler. The transducer is a couple of feet to the starboard of the engine, and sits about 1/8" inch below the bottom. This little boat is out of the water half the time but gives me extremely accurate readings.

I use it on the 11 to scope out new gunk holes, then take my Downeast Cruiser that draws 3 1/2' of water up them.

Thus, check the transducer placement before spending any money - your unit is probably fine.


Riverwhaler posted 06-14-2007 09:40 PM ET (US)     Profile for Riverwhaler  Send Email to Riverwhaler     
I have taken all the suggestions to heart and checked the alignment with the bottom. The transducer is now flat with the bottom of the boat. My problem maybe that it is mounted near one of the ribs near the center of the boat not as one of you have it two feet to the side. Went out on river last evening and ran to 40 MPH with not a missed reading. Guess I have to keep it perfectly flat. Thanks for all your suggestions.
Riverwhaler posted 07-03-2007 08:30 AM ET (US)     Profile for Riverwhaler  Send Email to Riverwhaler     
Ok here is the resolution of this situation. Was on Maine coast all last week with sounder being intermittent the whole time. So went to Hamilton Marine and got a new one same size and all.Replaced everything. Yes everything works well now. I think it was the transducer. But for $100 the fix was quick and easy. I may have left the sounder on for a time while the boat was out of the water. Don't know if that matters but.
Whale1 posted 07-03-2007 09:26 AM ET (US)     Profile for Whale1    
I have a 90 buck Humminbird on my Sakonnet that works well. Maybe I got lucky with the transducer placement but simply followed their installation instructions. It is on the starboard side of the transom parallel with the bay bottom, not the boat bottom.

The manual does say the transducer may be damaged if the unit is turned on while out of the water.

jimh posted 07-03-2007 03:12 PM ET (US)     Profile for jimh  Send Email to jimh     
Running the SONAR with the transducer out of the water is not a good idea. Think of the transducer like a drum. The electrical pulse is like a heavy mallet hitting the drum head. When the transducer is in the water, the drum head is dampened by the water, so the force of the electronic "mallet" is trasmitted through the "drum" and into the water. When the transducer is not in the water, the force of the "mallet" may be too powerful for the transducer (or drum head) to absorb, and it may be damaged.

If you left the SONAR on for a long time when out of the water, you very well may have damaged the transducer.

Casco Bay Outrage posted 07-04-2007 08:32 PM ET (US)     Profile for Casco Bay Outrage  Send Email to Casco Bay Outrage     
Allan -

Glad to see you solved your problem. Hamilton Marine is a great place.

Hope your time on the coast was good.



Brian7son posted 07-05-2007 01:08 PM ET (US)     Profile for Brian7son  Send Email to Brian7son     
Regarding the transponder not giving you a reading at all sometimes, there are some other factors that can cause that. They may or may not be involved in your situation. One is bubbles and/or churned up silt/sand from other boater's wakes. If you are in a busy channel, traveling behind a boat or boats that have churned up the water leaving a trail of bubbles and/or stirred up silt, that can cause your depth finder to have a blank reading or show something crazy like 900 ft. My unit also has problems registering depths under 2.0-2.5 feet while underway. It's mounted on the bottom lower half of my step hull, so it's actually about 1.5 feet below the surface to begin with. However, when it gets that shallow for my 285 Conquest,it's time to turn around or change course.
A Little Madness posted 07-10-2007 07:27 AM ET (US)     Profile for A Little Madness  Send Email to A Little Madness     
We had the same Hummingbird on our Classic Montauk w/the same problem about incorrect depth readings. I don't think there was a location on the transom that I DIDN't put the transducer and never got a good signal above 15 mph. My wife requested the unit be removed and the small sledge hammer brought out from the basement!

We recently purchased and installed the Lowrance LMS 527cDF iGPS Color Sonar/GPS w/internal antenna feature, so it's on the top of the dash. It obtains signal w/i a few seconds at most, and w/the NauticPath USA Marine Electronic Charts you get fantastic and up-to-date details. I've never lost signal either, regardless of how fast I was going or that I had the bimini up (w/stainless frame). The actual color presentation of both GPS & Fish Finding is excellent. Of course I'd like a bigger screen, but it is a Montauk, not a 23 Outrage. Probably the most impressive feature is the Dual frequency 200/50 kHz Skimmer®transducer which was installed in the very first location the Hummingbird was. For the first time I can be on a plain anywhere from 20 to 40 mph and accurately read depth, as well as seeing fish. I realize that at that speed I'll hit it before I'll see it on the screen, but the point is the stability and accuracy of the transducer. Never thought I'd spend that much but if you're considering this price range (approx $600+ depending on where you get it) I highly recommend this unit! I do not regret the decision. Good Luck

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