transponder placement question

[MAW31]

bought a used boat that has a Humminbird fish/depth finder with 2 transponders.

the bottom of the transponders are located just below the rear hull bottom.
maybe half an inch.

now this is the very first depth/fish finder i've ever had, but the depth readings are rarely accurate when its real shallow (3-4 feet) at any speed.

i've got a 18ft CC with a 90 evinrude.

Does it sound like the transponders are at the correct height? cause if i'm moving at all, they seem not to work.

are you 'supposed' to be still before they can be used?

 

[Silvertip]

Re: transponder placement question

Fish finders in that shallow water may not provide accurate readings. Some locators are also not very useful at high speeds but most should operate fine on most recreational boats. Transducers cannot be paralleled so if they are tied together, that's part of the problem. If only one is being used, then try the other. Also make sure the transducer is mounted properly. They need to be mounted solidly enough that they don't kick up at speed, but not so tightly that they don't kick up when hitting a weed bed or other small debris. Mounted too tightly they will break off when hitting something.

 

[MAW31]

Re: transponder placement question

thanks for your reply.

speaking of the transponders...they are side by side(one big, one small) next to each other and goto an A/B switch that says wide/narrow.

I'm guessing that wide means the scan angle is broader (and thus less accurate) and the narrow setitng is more of a 'straight down' view (and thus more accurate).

Is one better than the other with regard to depth readings?

 

[Silvertip]

Re: transponder placement question

Shouldn't make any difference as far as depth is concerned. They will make a difference as to what you see on the locator in shallow vs deep water. Look at the beam like an upside down cone shaped paper cup. In very deep water a wide angle beam would be covering a very large area whereas the narrower beam would be covering the area under and closer to the boat. you would likely use the wider beam in the very shallow water you mentioned. I would also disconnect each transducer from the switch and connect one of them directly to the locator and see how it performs. Then do the same with the other. It may be the switch itself is the source of the problem. It may also be that the locator head unit is not compatible with one or the other of the transducers -- heck maybe even both. You never know what some folks try.

 

[MAW31]

Re: transponder placement question

awesome. thanks.

I'm going out today, so i'll try a direct connect on each.

 

[John_S]

Re: transponder placement question

That is a good way to help diagnois and eliminate the switch. Depending on how they have run the wires for the switch and transducers, it might be rather difficult to do the test recommended by Silvertip. The HB switches I am familiar with has a section of cable built into the switch. To test each transducer seperatly, you would have to run them back up to the mount system. If everything is open and close together, it should not be a hassle.

Depending on which model of HB you have, you might have to turn off the unit, switch to the other transducer, and then turn the power back on. This would be for units that auto-detect transducer. Other models, you have to go into configuration screens to change them. There is also a chance, it might not matter, but would resort to the off-switch-on method. It might even have the wrong transducers, as Silvertip mentioned. If you provide the HB model, I might be familiar with it or be able to look-up some info. Pictures, pin-out, and any model numbers of transducers would be good, as well.