Fish Finder Depth Issues

[youngy555]

Had an old Lowrance fishfinder which drove me up the wall one to many times so Installed a hummingbird Fishfinder a few weeks back, its a decent one, colour screen, all the crap, I have it currently positioned where the install pamphlet told me, just below the hulls bottom and continue to get varying depths when above 20knots, im talking 0-50m and even more sometimes when i know the bottom is flat. when slowly moving it works a treat. i've found that when the water is choppy or its a bit rough, this seems to be even worse when cruising along, is there a remedy to fix this problem, anyone seen and/or fixed this before? Was trying to explain my drama to a wild character the other day and he insisted i mount it at least 6 inches up from bottom of transom? i presume he was out his tree because i have never seen a transducer mounted that high before, any suggestions, cheers

[johnno]

the only thought i would have is

My garmin said to mount the centre of the transducer

which was about 12mm below the hull from bottom of it

Did you mount it working of the low side of the hull

maybe you want to tip the transducer down further so you get more area in the the water and will hang in the water better at speed

if you are getting air under it ,it won,t work are you getting any disturbance off the hull which maybe causing it.

It may sound basic but i am just giving some ideas

[youngy555]

might have to spend an hour or so on the water changing its postition until i find a happy medium, thanks johnno. so the transducer on yours is below the hull by 12mm you say?

"My garmin said to mount the centre of the transducer

which was about 12mm below the hull from bottom of it"

[johnno]

Yes correct

[andrew399]

this happens to mine in choppy water also. Its because the transducer is installed to high up and when the boat rocks it comes out of the water. i couldnt be bothered changing mine though!

[youngy555]

Yeah i will try adjusting the speed next time. Just reading an article in the latest clubmarine mag and i'm pretty sure it says to have the transducer pointing straight down (perpendicular to hull), i dunno whether i have been misinformed but have always thought and have seen on other boats it pointing parallel with the hull, straight back, i suppose it makes sense to be pointing down?

[Brian]

I've had the same problem on my old Humminbird but, I have a newer one now and it's been great but, it took a lot of fine tuning. The type of hull will also make a difference depending on the shape of the hulls grooves and how well it sits in the water. A tinny for instance will get more air/turbulance under it and cause the transducer to miss-read at times as apposed to a heavy glass hull that may sit deeper.

The transducer itself must sit flat to the water ie: 90 degrees or your field of view will be at what ever angle it is set at. Think of one of those cone shaped looking glasses and you are looking off the back of the boat, thats the way the bottom will show up. If it's forward back or sideways that's what you are looking at. Straight down is below the boat.

Mine is also one a sliding plate with a spring pin. I drilled very close holes, extra to the ones already on it, so i could lift it up or down a few millimetres at a time until I got the right setting. Also I can slide it up and above the bottom of the hull so it is safe when pulled up on the beach or moving it about at the ramp.

No matter how well it sits though it will occasionally go silly. The other option is in hull fixing but a bit more complicated and not adjustable.

That's my experience anyway.

BP.