Depth Finder questions

Doc

Liquid Addiction
Staff member
Both my Four Winns 20ft open bow and my Baja Force (25ft) came with depth finders. Imagine my surprise when we got a 50' Gibson Houseboat last year and it didn't have a depth finder. I suppose it's because the Gibson is an 87; older than either the Four Winns or the Baja.

So now I'm wondering where to depth finders normally go on a 50 ft boat? I was considering two depth finders. One for the front and one for the rear. If I go this route where is the best place to put the sending unit? I plan to get the through hull type so that no holes will be required anywhere (I hope).

Thoughts?
 

waybomb

I'd rather be blown
If you worry about depth, like I was, I had an Interphase forward scanning sonar on my 42 Carver (48' loa). I never got into trouble. They have pretty concise instructions on where to mount the transducer.

On my Cougar I have a simple Gafrig depth gage.

The Interphase scans in an arch from below your boat to forward of your boat. It uses a phased array - there's no moving parts. You need to practice "seeing" obstacles, such as old pilings, but once you figure it out, it helps a bunch.

If I were on a river, I would certainly use an Interphase scanning sonar. Much better than a regular down-looking depth finder.
 

Doc

Liquid Addiction
Staff member
Very good point Fred. I'll check them out. Thanks! :thumb:
 

waybomb

I'd rather be blown
Did I mention - not cheap as compared to other depth finders? But look at the possible savings. If you have inboards, a bottom hit could nail a strut into you hull, sinking her. Or bending a shaft, rudder, and prop.

Might actually be cheap insurance on a river.
 

Doc

Liquid Addiction
Staff member
Well, I still have not bought the Interphase forward scanning sonar. I see refurbished ones on their web site for 799.00. More than I want to spend.
So, I'm back to square one and want a basic no frills depth finder that does not require me to drill any holes in the boat.
I actually need one for my Baja and the Gibson. The Baja has an outside mounted unit but it hit a stick or something and is now whopper-jawed. It works sometimes but can be a hassle.
Any recommendations for basic depth finders?
 

Doc

Liquid Addiction
Staff member
Thanks for the ebay link/search.
I've never drilled a hole in below the water line on any of my boats.
And I thought technology had the thru hull ones working as well as the outside hull ones.

Please educate me ....is it better to drill? Are they hard to install?
The one that's gone bad on the Baja was on there when we bought it.
 

waybomb

I'd rather be blown
I have no problem drilling the hull. The instruction with these things are fairly complete. First you need to locate it where the mfg says to. Drill the hole. Make a backing plate out of 3/4" marine plywood. Cut a hole in it. Bed the transducer and the plywood with 3M 5200. Crank down on the housing nut. Let the 5200 dry. Don't get any on the face of the 'ducer.

By the way, get a transducer that can be replced without replacing the housing. If you do it this way, you won't have to worry about getting 5300 on the face of the transducer, and, if the transducerreplaced ever goes bad, it is simple to replace. 5200 is some badazz chit!

Then run the wires up to the instrument.

Get it in the water at a known depth. Adjust the offset (the difference between the transducer location and the top of the water or the bottom of the boat, whichever floats your cork).
 

Doc

Liquid Addiction
Staff member
Good info Fred. Thanks. So .... I might just be able to replace the transducer, right? The one there now works, but the mounting tabs on one side of it are broken off. It will work but gets turned easily. I can point it back in the right spot but it never stays since it is lacking tabs on one side.
I'll find out what make it is and see if ai replacement transducer is available with the same hook up as far as teh cable goes.
 

waybomb

I'd rather be blown
Yes, if you want to just replace the transducer.

You don;t even need to buy the same brand. Your manual should tell you what frequency your transducer is. If it does, and the manual shows the schematic, you can buy any transducer with the same frequency, so long as you can get a schematic for it as well. You'll want to run the wires into your units original plug if different. If you are going to spice, solder, stagger the joints, make sure you cut back enough of the wires so the shield is long enogh to cover the entire length of the splice.
 

Doc

Liquid Addiction
Staff member
I do not have the manual for the current depth finder. Don't even know the make of it. I can do some digging around and hope the company is still around and offers manuals online. It appears to be an add on, that did not come with the boat originally.
 

Bt Doctur

Super Moderator
Staff member
Like waybomb says, adjust it for the difference or measure up from the bottom most part of the boat to the transducer and subtract that from the reading to get the true bottom of boat-to- actual bottom
 

waybomb

I'd rather be blown
count the number of knots that go overboard during a 30 second period. This is your speed in knotsiftwood t. You do not need any LCD screen, or and such frivolous contraption.
Well that would really suck - I'd need at least 4,840 feet for a 30 second measurement. Practicality comes in to play.
 
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