Sonar question

[hitthebricks]

When I motor in to a area and check out the sonar I'll see fish and figure it looks like a good place, shut the motor off, troll around with the electric, but I don't read to much anymore on the sonar, get ready to leave, fire up the motor again and start to leave and there is fish everywhere again. WHY?

[John McCann]

sounds like your transducer is too close to the motor. bubbles and such is distoring the response.

[Surface Tension]

Where is the sounder getting it power from and what else on that battery? If you have a volt meter on your sounder see how many volts you have when running and compare that to when the problem shows up. Could be that you getting a voltage drop from a weak battery after the main engine is shut down or the trolling motor is turned on. That voltage drop if significant, is like turning your gain down.

Where is the transducer mounted?

If the ducer is mounted to close to the motor or on the left side of the boat(prop rotation)it can throw turbulence at the ducer.

[hitthebricks]

Well guys, The transducer is mounted on the right hand side and about as far away as you can get. The readings I do get when the moter is running are not the interference type but archs relating to structure or baitfist or depth changes. I think you described it well with "its like turning down the gain". I have a new starting battery and thats what powers everything but the trolling motor. I'll have to check the connections for a voltage drop or poor contact. Thanks HTB

[hitthebricks]

I checked the voltage with a multimeter and I have 12.5 volts with the motor off or running. Would it appear like that because I'm moving slower with the electric 1/2-1 mph vs. 3+ mph with the 200? HTB

[Jim Hudson]

Hit

What is it do you not read anymore? Fish as in arcs? Do you loose bottom? If your over weeds, does it still show these? And what kind of sonar is this?

[hitthebricks]

OK, I pull into area and see fish relating to breaks or active around schools of baitfish, start up the trolling motor and never see that again on the sonar. I talked to a buddy tonight and his claim was "the fish are active and disperse as you go over them" so they don't display on sonar. Buy the way, does a tm scare or disrupt active fish? I'm using a Lowrance 480LMS but all I read is bottom, but no fish type arcs when hunting for fish and using the tm for power HTB

[countryboy9799]

For me its the opposite. I think my outboard scares the fish away especially in shallower water. I always mark more fish with my elec. trolling motor. You could try drifting for awhile where you think there should be fish and see what happens. If you mark fish drifting then I would wonder about the TM.

[Jim Hudson]

Arcs usually turn into straight lines when you are not moving or moving very slowly with a trolling motor from my observations... You still should be able to see that.. As long as you graph still shows good definition of the bottom and still shows other structure like weeds, rocks, etc I would believe your graph is fine..

[andy j]

Jim is right most of the time you see archs when you are slowly moving and will see longer horizonal marks when you are not moving or moving very slowly, this is because the fish stays under the cone angle longer which results in a longer mark. if a fish camps out right below your tranducer you will get a continuous horizonal mark until the fish leaves the cone angle.

[hitthebricks]

Sounds like a good answer, I'll have to ceck it out when I get out next time. Thanks for the replys HTB