Need Help, very strange transducer reading issue

Hi all, looking for some help here. My brother bought a 96 Smokercraft Stinger 161 with a Johnson 90 2 stroke.

No matter what we do we can’t get a bottom reading of any sort at any kind of speed. It reads just as it should when sitting dead in the water or at idle. Give it any throttle at all and instantly start losing bottom signal. The best we’ve been able to get it is to give a very thin bottom signal cruising at about 20 mph. Any faster and it’s gone. If you burp the throttle the throttle at rest the bottom will weaken, then come back as soon as you let off the throttle. The boat moves very little and doesn’t gain any speed when doing this. This is leading me to believe there is something happening with the prop wash/lower unit frequency rather than bad flow of water under the boat.

We’ve tried 4 different transducers on 2 different sonar units. Moved the ducers all over the mounting board, and adjusted depth from skimming the surface to as deep as we can possibly put it. Have also adjusted the clicks to tilt the back up and down from tiled up too high, to perfect, to lower than you think. For the most part nothing really changes the reading.

Best reading is with a skimmer transducer set deep, and actually tilted away from the motor, mounted on the starboard side and tilted towards the right. Also get a slightly better reading when turning the boat left. We were shocked to see how far starboard had tilted the ducer when we pulled the boat out (ducer mounted on starboard side). Only thought is doing this directs the beam away from the outboard, which must have some bad frequency going on or something.

We’ve isolated all wiring by using an external battery with nothing but the power cord hooked to it, and have also run transducer cables on the floor of the boat to keep that away from any other wiring, even holding the cord up away from the boat.

We have the ducer mounted away from lines of rivets, ribs, etc. I’ve setup a few boats with transducers, my uncle has done several over the years, and we’re all scratching our heads. Based on everything we’ve done, we’ve nearly ruled out bad transducer placement, and are wondering about some strange frequency from the motor.

With all that said, has anyone experienced anything like this before, and do you have any suggestions of things to look at to resolve this?

P.s. the outboard plugs and wires have been replaced. The transducer issue has not improved since doing so.

Thanks for any suggestions.

Tucker

What graph do you have?
Post a picture of the transducer and location

We’ve used both a Humminbird 999 and a Helix 7 G2N. We’ve tried 2 DI Helix transducers, the 999 SI transducer, and finally purchased a skimmer transducer for the 999 which should give us the best chance of getting readings at speed. I only have 1 bad pic of the last transducer location, but understand that I know being mounted like this is not correct.

Stabdard transducer mounting depth and angle does not give good results. Really nothing does, but somehow this extreme sideways angle is better than anything else.

Attached is actually the best we’ve found so far. Notice how far to the right the ducer is tilted. It’s surprising it even works. That angle has to be compensating for some issue with the boat/motor.

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Did you read the owners manual?

Lift it up about 3″.

Then have the front barely under the hull and ass end tipped down a few degrees.

Transducers are meant to skim, not be buried in the water (unless they a through-hull)

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Yup. Not a novice with setting these up. I wrote a novel in the 1st post so it’s probably hard to read the whole thing. Setting it up correctly in various locations on the hull gives no improvement and is actually worse than where it is in the picture.

The only way to get any reading at all is to set it very deep and surprisingly that starboard tilt is an improvement over parallel to the waterline. I’m surprised the way it’s set in the picture even works at all.

Something very strange is going on which is why I’m seeking online help. Everything that has worked on any other boat doesn’t work – at all, on this one.

I don’t believe it’s a dirty water under the hull issue. As soon as you give throttle the bottom is gone. It isn’t an outboard rpm issue either. Revving up in neutral doesn’t give any interference at all. Burp the throttle in gear from a rest and the bottom thins out and disappears.

I would set it up like bmans picture. Then adjust the graph from there. Reset the graph to factory settings.

Are you using any extension cables or connectors that could be loose or faulty?

We have had it setup like Bman has in his picture. It doesn’t work. At all. Not even a little. No amount of changing settings, sensitivity, surface clutter, frequency, etc shows any improvement.

There are no extensions, not routed by other wires, nothing to interfere from an electrical standpoint. We’ve even resorted to running an external battery sitting on the front deck with nothing but the power cord connected, and the transducer cable is not routed through anything on the boat, just sitting loose on the deck and floor. Not running near other wires, nothing.

We’ve given this every chance of working. 2 of us that have a fair amount of rigging experience have worked on it for hours and have seen little to no improvement.

Could anything with the prop or lower unit (bad bearing etc) be giving off some odd frequency that’s giving us fits? I even tried a ferrite ring on the ducer cable with no improvement.

Have you tried a different transducer? When setup per the instructions (or bmans picture), it should read good, with only fine tuning needed after that.

We’ve tried 2 helix DI transducers, an SI ducer, and finally a skimmer transducer. The same thing happens with all of them.

I have no idea, wish I did, but for the poor man’s sake, read the post… it ain’t working like it should, even when mounted correctly, and wired in such a manner as there can be no interference, which is why he needs assistance with what is an unusual circumstance.

All I know is that di or Si transducers will not give any reading as a rule over 6 mph. They work best at 3 to 4 mph.
Getting a skimmer to work is the only way to get any reading on plane.

post picture of bottom of hull to show what is in front of transducer.
Could be a strake or rivets interfering with water getting to transducer.

Wildlifeguy wrote:

I have no idea, wish I did, but for the poor man’s sake, read the post… it ain’t working like it should, even when mounted correctly, and wired in such a manner as there can be no interference, which is why he needs assistance with what is an unusual circumstance.

Yes! Thank you, lol!

This is very unusual and we are tearing our hair out.

mxskeeter wrote:

All I know is that di or Si transducers will not give any reading as a rule over 6 mph. They work best at 3 to 4 mph.
Getting a skimmer to work is the only way to get any reading on plane.

Yup. I talked my brother into buying the skimmer transducer. It has given us the “best” reading which is what you’d expect. Unfortunately best is very close to non functional.

eyekatcher wrote:

post picture of bottom of hull to show what is in front of transducer.
Could be a strake or rivets interfering with water getting to transducer.

I don’t have the boat at my house to post a pic, but i can assure you we have avoided ribs and longitudinal lines of rivets. The hull is not dented, creased, or formed in any unusual manner.

I’ve been rigging boats for 20 years and my uncle over 40. We’ve always been able to eye ball placement like Bman posted, get a reading, and then fine tune for best readings from there.

This case is a whole different animal. Something odd is happening.

To give an example of skill set and understanding of transducer placement, my uncle is running a Helix 10 mega SI with only the big SI ducer and gets bottom readings up to WOT which is about 35 MPH in his Alumacraft Voyager.

Couple things…..can you get a reading if you unhook the ducer from the board and just hold it in the water? Does it work at all even at a float?

Next option would be to rig it up on another boat. If it works on another boat it’s the boat that’s issue.

Matt Moen wrote:

Couple things…..can you get a reading if you unhook the ducer from the board and just hold it in the water? Does it work at all even at a float?

Next option would be to rig it up on another boat. If it works on another boat it’s the boat that’s issue.

Good questions. It reads perfectly fine at rest and idle speed at around 3 mph. Start giving it any throttle to plane and the bottom inmediately thins out and usually disappears, no matter the sensitivity. Pretty much if you slowly increase throttle it’s getting pretty bad by about 6 or 8 mph. Give it any normal “get on plane throttle” and it’s gone about immediately.

However you can rev up all you want in neutral with no interference or issue. Seems to be something with the prop/lower unit turning.

We tried rigging it to a 1×2 and holding it in the water by hand while on plane but couldn’t keep it in the water properly.

The 999 is my old unit I sold to my brother. I had it in a glass boat so my ducer was glassed in, but everything worked perfectly. We tried the Helix 7s he bought from a co worker as well and all symptoms are identical.

Well you have us all scratching our heads

Out of curiosity, have you gone WOT and hit the kill switch? Does it read on-plane without the motor running?

Have you tried running it on the port side by chance?

Haven’t tried that yet, Bman. But, as we let off the throttle the reading does improve with the boat still moving faster than it would when coming out of the hole.

At one point we rigged a transducer up to a board and clamped it to the transom. I think we did try it on the port side and if anything it seemed worse. But its so bad it’s sometimes hard to tell what’s better or worse. The design of the back of this boat doesn’t make clamping a stick/board to it real easy but we made do while running some experiments.

We’ve been at this off and on since early May and so far nothing has shown much improvement other than the crazy transducer placement I posted in the picture above.

Everything im reading sounds like cavitation problems.
I suggest 16″+ away from the motor…i.e. move it further starboard.

Everything works stationary but fits underway is usually cavitation.

Have you actually tried a reset as was suggested? Was having issues with mine intermittently loosing signal after about 2 years use. Checked the settings and everything seemed ok, reangled the transducer one notch ea way, called Humminbird who said maybe a week transducer, and considered putting in a whole new locator. The other day out trolling it started acting up at trolling speeds and I had enough. looked through the menu and saw the reset option and figured I had nothing to loose. Selected reset and locator works like new. Really don’t remember ever making any setting changes that would affect anything, yet after reset everything works. I really think it was something that had gotten out of wack in the unit itself that the reset fixed. Only downside to trying reset is that some settings need to be reset to your liking such as heading.

From your description you are almost certainly getting electrical noise from the motor itself. It could be the lower unit, or interference from the motors electrical system itself. A spinning lower unit does have a magnetic field that is generated due to the spinning mass. Normally it doesn’t have an impact, but there are the rare cases which can create issues. I saw an issue once with an early etec G1 lower unit causing problems, not near as severe as what you’re describing though.

Have you tried the noise filter? Step through those settings, it’s purpose is to try and help deal with engine noise.

FishBlood&RiverMud wrote:

Everything im reading sounds like cavitation problems.
I suggest 16″+ away from the motor…i.e. move it further starboard.

Everything works stationary but fits underway is usually cavitation.

This could be. I wondered if dropping the transducer so deep and tilting it in such a severe angle only showed improvement by getting it further away from the issue, whether that’s the lower unit, cavitation, etc. Maybe we need to mock up our stick again and clamp it on the outer edges of the transom and see if it gets better.

Musky Ed wrote:

Have you actually tried a reset as was suggested? Was having issues with mine intermittently loosing signal after about 2 years use. Checked the settings and everything seemed ok, reangled the transducer one notch ea way, called Humminbird who said maybe a week transducer, and considered putting in a whole new locator. The other day out trolling it started acting up at trolling speeds and I had enough. looked through the menu and saw the reset option and figured I had nothing to loose. Selected reset and locator works like new. Really don’t remember ever making any setting changes that would affect anything, yet after reset everything works. I really think it was something that had gotten out of wack in the unit itself that the reset fixed. Only downside to trying reset is that some settings need to be reset to your liking such as heading.

Have not done a reset. Losing pre set settings is not a big deal. I’d be surprised if it worked, being that 2 units have shown the same symptoms, but it could only help. We’ll do a reset next time out.

I agree with FBRM. Need to move further away from motor.

Sounds like to me that the rectifier/regulator is bad in your charging system and you are getting AC voltage into a DC system at upper rpms.

Hook a voltmeter to the positive wire at the starter solenoid and the other wire to a good ground.
set the voltmeter to the AC function.
If you get a reading of over 2 millivolts AC above a high idle you have a problem in the charging circuit.

And then there is Iowa boy who probably knows more about this stuff than all of us combined. ^^^

Ripjiggen wrote:

And then there is Iowa boy who probably knows more about this stuff than all of us combined. ^^^

Yup, Iowaboy from the toprope.

Getting good suggestions. And I was hoping Iowaboy would respond.

We’ve used a separate lithium battery sitting on the deck in front of the console with only the power cord hooked up to it.

We can also rev the motor up as much as we dare in neutral with no loss of signal or interference. Would you still suspect a bad regulator could cause this?

Either way I sent my brother the steps to check it.

AC voltage and ignition interference can do strange things to electronics.
I can’t explain how it works but I do understand how it does so follow along with me here.

When interference is generated it can use the entire boat as an antenna.
How?? On aluminum boats your motor is grounded to the hull simply by being clamped to it,the interference uses that ground as the pathway to the hull turning it into an antenna.

I know that sounds bat poop crazy but I have seen it before.
If the charging system checks out you could have an ignition system problem on the secondary side that only shows up under load,IE, when you are in gear throwing the coals to it.
In other words a coll,a spark plug or wire is leaking several thousand volts to ground and creating the problem.

You would think the motor would misfire but not always until it gets bad enough to show up.
Resistor plugs may help but they can cause a crappy idle which I have seen numerous times.

Have someone perform a full charging/ignition system check with a good volt/ohm meter and use the DVA adapter when doing it or you are waisting time without it.

Hope that helps you out.