Hey all!

I am having problems with my new HumminBird 581i combos transducer. It is transom mounted and is not reading right. First off the depth keeps jumping around and won't settle on one depth. Also, it reads wrong because it was saying 3ft today and i could not even touch the bottom with my 7ft rod. It does not show the bottom on the screen(i think) either. It kind of just looks like grass everywhere on the screen from top to bottom. I already adjusted sensitivity and all other settings i thought would help with no luck. The transducer is mounted a bit lower than the instructions say but i did not think it would matter. I added some pictures of the transducer mounted to see if anyone can tell if i mounted it wrong.

The only thing I could think of off the top of my head while looking at your pictures is transducer placement.  That first picture looks like you have the transducer sitting right behind a chine (or whatever you want to call it) on the hull.  Could you possibly be having a bunch of bubbles accumulating in that spot throwing off the readings?

I just ran my HB for the first time yesterday. It did the same exact thing for about the first minutes. I eventually started getting good readings when I reduced the sensitivity to one.

BTW I want to make sure the depth it's indicating is correct now. On some spots where my Lowrance always indicated 11' the HB is indicating 9'. The water on this lake does not change so its time to get out the weight and rope and see which is correct.

I am leaning towards attaching to the inside bilge area with epoxy(should have done that in the first place). Would it work about the same accuracy wise?

To get any reading above a slow idle, the bottom of the transducer has to be level or just below the bottom of the hull. You have it on the step and not the hull bottom. It should work fine at slow trolling motor speeds or sitting still like you have it.

To get any reading above a slow idle, the bottom of the transducer has to be level or just below the bottom of the hull. You have it on the step and not the hull bottom. It should work fine at slow trolling motor speeds or sitting still like you have it.

It won't even work right sitting still!

The only thing I could think of off the top of my head while looking at your pictures is transducer placement. That first picture looks like you have the transducer sitting right behind a chine (or whatever you want to call it) on the hull. Could you possibly be having a bunch of bubbles accumulating in that spot throwing off the readings?

Thats what I am thinking too.  More than likely there are air bubbles getting in the way.

But air bubbles even sitting still with no wind!?! Could it be the transducer doesn't work?

But air bubbles even sitting still with no wind!?! Could it be the transducer doesn't work?

Both of those are really possible.  It can't hurt to swap out the transducer if you can.  I'm sure you don't want to drill more holes into the hull.  But you'll have to drill anyways if a new one doesn't work.  You could opt for the shoot through hull, I know you've said you fish shallow lakes for the most part anyways.  That may not be a bad option.

I think i am going to seal the holes and get a shoot through.

I think i am going to seal the holes and get a shoot through.

You will be glad you did, especially in Florida, with the weeds......Al

I have had some irratic reading with mine from very soft bottoms. For a fiberglass boat I would put the transducer inside shooting through the hull. Mine has been there for well over 10 years and still going strong. Good results up to 50mph and highr if the lake is not too deep. I lose signal at 50 and over 150' deep.

I hear the transom transducer/skimmers don't do well in the bilge because they are not designed to be there?

Just a thought. Are you running any other depth sounder at the same time? This will cause interference.

No just one because my bow unit messed up so i have just the GPS one.