Graph not reading at speed

[Hower08]

Not sure if title makes sense. But once my boat gets up around ten mph or so my graph goes all crazy Stops reading and give me crazy depths and what not. I know it's from the turbulence of the boat just wondering how to remedy the problem.  Its an older humminbird unit 

[jaimeastin]

I just fixed the issue for my boat.  I would lose readings at 6mph.  I moved it farther away from the center and prop.  It saw increased reading up to 10.  I kept working outwards and for a sweet spot.  Now I get reading up to 10-20 mph that I can use for scouting.  I get depth readings on plane at 27 mph as well.  

[TOXIC]

"Normally" if you want on-plane accurate readings, you need to mount a transducer in the bilge for a shoot-through reading.  Since side scan and down scan aren't designed for on plane readings, I use my 2d sonar while on plane and it works well.  

[MickD]

My experience with the same troubles on a new Humminbird Mega Imaging transducer is 1.  You can make it work properly by locating it exactly right, depth and tilt, but it's hard to find that sweet spot.  2.  Another transducer can be added.  

 

I'm not sure my experience translates to your transducer, but that's what I went through.

 

 

[Hower08]

I'm not sure how a shoot thru would work on an aluminum boat I will look into that. This is a 2d sonar as I have not yet upgraded to a SI graph at the console yet. I know this is a common issue with graphs you would sure think it would be easier to combat. And my transducer is almost all the way to the right side of the boat. 

 

I think I will do like suggested and try to get it as far away from motor and then level the transducer with the boat

[Tim Kelly]

The transducer needs to be in the water and free of turbulence to give good readings. If your TD is right at the edge of the hull it might not even be in the water when you're on plane. Put a big transducer mounting board on the transom and experiment with different positions. Read the humminbird manual for positioning, it will be relevant even if your unit is an older one. you can almost certainly get it working to 20mph or so and quite possibly up to full speed depending on the hull.

[Hower08]

My boat only runs 24 mph or so with me in it. I'll take a look at where the ducer is at and report back with some rough measurments or even a pic. I will also try to find the manual online or possibly even read the manual from my Helix 7 

[WRB]

It looks like the right corner edge of your adapter plate is below the hull plane surface and that will cause you problems with air bubbles. The TD can't be inline with hull stiffeners or any surface that causes turbulence. You OB propeller shouldn't be and issue as it sits at least 6" behind the transum. 

Your TD looks like a SI unit?

Tom

[Hower08]

The photo above isn't mine. I'll mosey on out to the garage and have a look at the TD and report back

[Hower08]

Won't let me upload photos if someone has an easy way to do it I could send pictures. The TD is clear of any chines or rivet lines under the boat. Center of the TD is split by bottom edge of boat and TD is almost 3/4 of the way to the edge of the boat from the center of prop

[MickD]

Sounds by your description that you are very close.  Leave it there until you're on the water again, then when on the water move it down just a little, eighths of an inch at a time.  When I used to cobble my transducer to a boat provided by the resort it would make a lot of splash if too deep, but it would read correctly.  When I got it right it didn't make much splash but still read correctly.  If too high, didn't read.

 

You might have someone else drive the boat and observe if you have an obvious area of smooth water somewhere on the back of the boat while at speed.

 

Uploading photo files is easy if the files are not too big.  Set your camera or phone to low resolution to minimize file size, get the files onto your computer, then it's simply click the "choose files" and browse for the files on your computer.  Select them then click on "open" or "select" or whatever command your computer uses and they will load and be sent.  I can't help with sending from a phone.  My phone is smarter than I.

[Hower08]

Manged to get two pictures resized correctly. I will try to lower it before the next time the boats out. I'm out with a pretty serious injury right now so it will be a while before Im running her

[WRB]

Should be even with the bottom of the boat, it looks about 3/4" below or too deep creating turbulence and a lot of spray.

Tom

[Dogface]

I have a similar problem. I use a SI Hummingbird. I purchased a second finder. It works when it wants to and is not reliable at high speed. The transducer is mounted on the stern like those pictured. The instructions say I can mount it in the bilge of my aluminum boat. They say if the metal is less that 1/8" thick the transducer can shoot through the hull.  

 

I will try it and if it works I'll glue it in place.

 

The transducer is a Hawkeye and you can get info at hawkeyeelectronics.com or norcrossmarine.com. It was cheap. About $50.00.