Fish Finder Depth Gauge?

Prarie Guy

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So I am now the proud owner of a project boat StarCraft 18 ft SS and starting to think about how to equip it and find that I don't really know much about the current crop of electronics and accessories. I have searched the site but so far not found the information I was looking for.

What I want / need is something that will provide a depth reading at speed the northern lakes here can have rather abrupt changes in depth and I really want some warning.

The old fish finder I had provided depth underway it seems as if the new generation of fish finders may not do this, so the question is do I need both a depth gauge and a fish finder or do some fish finders provide real time depths while underway?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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and most have sonar now so you can see the stuff under the boat.
 

ondarvr

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But... the first warning of shallow water at speed will be the lower unit hitting the bottom. They don't show you what's in front of the boat.
 

Prarie Guy

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Ok I was under the impression that a lot of them did not provide readings when you were traveling 20 or 3 mph
 

dingbat

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Ok I was under the impression that a lot of them did not provide readings when you were traveling 20 or 3 mph
There is no physical reason for a sonar unit not to read at speeds of 30 mph. The biggest factor is the quality of the transducer installation, followed by poor "Q" value of transducer and the processing speed of the sounder. The latter two would only come into play at higher speeds
 

David Young

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Pick out the one you want from Amazon and read the reviews about them. I bought a Lowrance Elite 4 a couple years ago. It has a shallow water alarm that you can set to any depth you want. Everything displays real time, at speed. My old boat only does 35 mph but, gps speed and depth, displays all the time. Plus, its a chart plotter, fish finder and does water temperature. I love mine and has saved me a propeller more than once :)
 

Silvertip

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30 MPH is 44 feet/second. If your sonar is looking ahead to 300 feet that leaves you with 6.8 seconds to get stopped or turned away from the obstruction. Your brain will take 1 or 2 seconds or more to determine if there is a real problem or not and by the time it does that calculation the lower unit is gone. The Sonar is a great tool but it works best if you familiarize yourself with the charts for the water you run in. This is especially important where very abrupt and significant changes in depth occur. I was once running at 32 MPH in 75 feet of water in northern Minnesota. Keeping a close eye on the locator the bottom was flat as a pancake and I'm running between an island and the mainland. In a heartbeat the depth went to 7 feet and I expected the crunch that never happened. As quick as the depth went shallow, it went back to 75 feet. Than evening I pullled up a lake map and to my surprise, a land bridge existed before the outlet of the lake was dammed years prior. It was that narrow strip of land I passed over. In my case, the entire event was over in a couple seconds. Know your water -- especially water that is not marked with navigatoin bouys. If you run the Mississippi river up north you best be familiar with wing dams and the bouys.
 

ondarvr

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The typical low end unit doesn't show 300' in front at speed.
 

Prarie Guy

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Thanks guys not looking to tour a lake based on the depth finder but sometimes you make a mistake about where you are. Then it would be nice to at least have a chance to realize things are not right.
 

Fed

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You'd be better off with a plotter, look up the Chart Viewer on the Navionics website & stick the app on your smart phone or tablet.
 

ondarvr

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Mental note: "some" equals "they" and "they" equals = low end unit.
Got it....

Looks like that transducer works at up to 8 knots, and costs about $1000.

So like I said, at speed you're going hit whatever it is with the lower unit before you see it on the screen.
 
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dingbat

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So like I said, at speed you're going hit whatever it is with the lower unit before you see it on the screen.
Scary......border line negligence, that someone would put the life of their crew at risk knowingly full well they are traveling blindly at speeds in excess of their ability to react to avoid a collision. No different than running in the fog w/o radar
 
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