1991 280DA depth sounder question

[sryc2009]

I just purchased a 1991 280DA with 463 hours on a twin 350 power plant. I love the 10' 6" beam which was a big step up from 8' 6". :smt038 She is in great shape with beautiful lines. I have a question on the depth sounder which is a lowrance round dial mounted in the dash (stock). The sounder at start up in the shallows just flashes,but upon reaching about 10' of water it now reads just fine until I again reach shallow water. I have no information that came with the boat about how to set the sounder.Any advice would be appreciated. Thanks ...............

 

[Henry Boyd]

Welcome.

I know you covered the info on your boat in your post, but if you put it in your signature it will show up on all your posts, and help anyone trying to answer a question for you.

Speaking now in generalities. a depth sounder is an active sonar transmitter/receiver. When it is flashing it is telling you that you are in shallow water. (yeah you know that). What is happening is the the bottom is so close to the transducer that the echos are coming back faster that the receiver expects, or can process. The thing works by sending a sound pulse and then timing the return of the echo. It knows the speed of sound in water and then just does the math.

The question is really how deep are 'the shallows'? One foot of water between the bottom and the transducer would sound normal, or at least consistent with the Lowrance depth gauge we had, and the Raymarine sounder we have now. If the water is deeper might suggest the units is due for retirement.

Henry

 

[Cocktail Time]

Here is the link for the manual. When I had one of the same units you could set a shallow and deep water alarm and the unit would flash as you describe. You might be able to disable the shallow water alarm and get it going it will read less than 5 feet.

http://primus.lowrance.com/support/...m&result=0&excerpt=3500&resultType=5001#Goto6

Best of luck, Dan

 

[duman95]

Had the same issues on our 1990 280. I think it is just the vintage of the sounder coupled with the fact that it is not a through hull transducer but it is epoxied down to the hull. Ours would flash 5 all the time warning that the water was less then 5 ft which it was and then it would start to register around 7-9 ft.... It is what it is and it was annoying and did not instill much confidence... It was the next thing on the list to replace with a better system, but then we sold the boat...