Author Topic: Transducer, losing bottom at speed  (Read 3748 times)

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Offline Bergy1

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  • Location: Nebraska
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  • Unit(s): 899 SI, 859 DI
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Transducer, losing bottom at speed
« on: May 09, 2015, 11:22:53 AM »
I'm having trouble with losing the bottom at speeds over about 20 MPH. Depth does not matter.

Situation: New to me 19 Aluminum V-Hull. Dealer installed Humminbird SI transducer. I mounted a 2D transducer to help remedy the issue. I'm played a bit with angles and hope my current angle will work.

I'm running it on a Humminbird 899HD SI. The SI transducer was/is losing bottom at speed as well.

Does it matter whether I run Switchfire on Clear or Max?


Pics:

#1 is where it is located. The old holes above the bunk are from previous owner. I could move bunks forward and mount the transducer there.

#2 is the angle to which I have it right now, have not run it here yet, but have been close.

#3 a shot of the other side and possible better location?

#4 a shot of the underside of the hull. Not sure if those rivets further up are going to be an issue?

Any insight would be helpful.ila_rendered
« Last Edit: May 09, 2015, 11:26:38 AM by Bergy1 »


Offline Airliner9

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Re: Transducer, losing bottom at speed
« Reply #1 on: May 09, 2015, 02:03:07 PM »
I hope some people with more expertise than me chime in soon, but in the mean time I will offer my 2 cents.


The transducer located close to the center line seems too close to the prop.  Could be picking up a lot of cavitation at speed.

The outboard one seems to be above the bottom of the hull and again be getting cavitation.

Do you have enough play in the slotted mounting holes to drop the transducer a bit and see what happens?

The bunk sticking out too far from the back is a problem waiting to happen.  Maybe you can just slide your trailer winch back a couple inches to make sure you don't hit the transducers.

I've got the 899 too and don't have a problem with bottom readings at speed (31MPH by GPS) on my 16 foot Lund, with either my HD or compact transducer, but the 2D screen goes a little crazy to say the least.  But the back of my boat is pretty flat, which might have an effect at speed.
 For optimum angle on the transducer, you can fine tune that by looking at the fish arches.  (I just learned that a couple days ago)

Best of luck and keep tinkering with it.  By the way, does your Fish ID+ work?   Mine isn't, but I keep playing with it.

Offline rnvinc

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Re: Transducer, losing bottom at speed
« Reply #2 on: May 09, 2015, 10:09:46 PM »
My guess is the rivetson the underside of your hull are creating too many bubbles ...

You might think about installing a mounting board on your transom so that tweaking does require new holes in the transom each time ...

Left and right with this many rivets probably may not help much ...(like Airliner mentioned just stay away from directly in front of prop) ...

So back away from the transom (with the mounting board) ...and down more in water may be the best option ...

Rickie


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