My fish finder lies

[rusty barrels]

Just tried out my new hummingbird piranha 180 and when the motor is running it shows all kinds of fish but when I shut the motor down they seem to disappear.This seems to be common to my other units too. I own a paramont and a 383 that does the same thing. They do give a pretty accurate depth to the bottom tho. What gives?

 

[Splat]

Re: My fish finder lies

Do you have the transducer mounted properly?

This sounds like it may be due to cavitation, especially if you have 2 units doing the same thing.

Fish finders look for a small air bladder that runs along a fishes lateral line. They can identify this bladder as containing air because they return a specific echo when hit with sound. If your getting cavitation it possiable the transducer is picking up on the bubbles and thus returning an eco of a fish bladder.

You can also try backing off the senstivity a few clicks, or turn off fish I'd and learn to look for arches, these will be fish.

Bill

 

[rusty barrels]

Re: My fish finder lies

I've mounted them per instructions, And I'm not cavitating at 5 knots or less
I'll try the senstivity and turn off the fish i.d. (never used those features before).

 

[gss036]

Re: My fish finder lies

When you are running the unit is reading "AIR" bubbles, common on all units.

 

[Chris1956]

Re: My fish finder lies

Rusty, You should not be reading air at those slow speeds. Is it possible that it is electrical noise from the spark plug wires or charging system? Does it happen when you are in neutral?

 

[rusty barrels]

Re: My fish finder lies

I'll have to check that next time I go out Chris.

 

[John_S]

Re: My fish finder lies

If the fake fish are at the top of the water column, it may be air bubbles. I suspect Chris may be correct about the electrical noise issue. Any chance this is an old outboard running without resister plugs? Otherwise, examine the transducer cable, looking very carefully for any slits or cuts, including where routed through items. If the shield is cut you will pick up allot of noise. If you were running complete seperate units and not using same transducer, chances are the noise is in the power line. Try running it off a seperate 12v battery to confirm if the issue goes away.

 

[lowkee]

Re: My fish finder lies

The fish only feel safe when your motor is running. When you turn it off, they think you are going to begin fishing and scatter.

I couldn't help it, the title alone forced me to click on the thread

 

[rusty barrels]

Re: My fish finder lies

The motor is a 93 25hp merc. with resistor plugs. and the unit is the only thing connected to the battery, no other power reqiurements are needed yet.

 

[JB]

Re: My fish finder lies

I'll try the senstivity and turn off the fish i.d. (never used those features before).

You really need to read the manual, Rusty. What is happening is that with the engine running the voltage rises and the sensitivity increases to the point that it is returning false echoes. When you turn off the engine the voltage drops back to 12.6 and the false echoes go away.

Learn how to set the sensitivity and to read fish arches and you will be okay.

 

[HONKER1]

Re: My fish finder lies

Read this. It may clean up any question you have about a fish locator.
http://www.lowrance.com/en/Support/Tips-and-Tutorials/Sonar-Tutorial/
Particularly the "Final Notes on Fish Arches" You need movement between the boat and the fish to develop an arch.