GT40 ducer placement on an old beat up charger

[Ted Martin]

i bought a 93sv (no chirp) unit the other day on sale and it came with a gt40 ducer.

i have a 2-step transom, the lowest one is sort of a notch around the drains and intakes, then a second step up to transom/plate mount. you can see where i have the old-school lowrance ducer mounted - anyone have recommendations on the placement of the 40?

[Ted Martin]

My thought was directly above the old ducer on the very bottom of that second step.

Have you guys had any trouble with the factory mount in stumpy environments on a similar placement?

[Larry3215]

It needs to stay on the lower step or you wont get any readings at all on plane and crappy readings at any speed above idle. The lower step will cause too much turbulence.

[Ted Martin]

It needs to stay on the lower step or you wont get any readings at all on plane and crappy readings at any speed above idle. The lower step will cause too much turbulence.

wait - what? I assume you mean place it on the middle step? at this point, i plan to put it below the plate but above the lowest notch if that makes sense. or are you saying the lower step will cause too much turbulence if i put it above?

EDIT - well in any case it don't really matter, that lower notch is too shallow for the mounting bracket, the ducer would be hanging substantially below the pad, so i will have to put it on the one above and adjust it down if necessary. The only other option i can see is to move it off to the right but the bunks on the trailer could come into play there. I will go with bottom of the middle step, if that doesn't work out i will have to see about an attachment to the plate or something.

[Larry3215]

Anything at all in front of the transducer that disturbs the flow of water will cause turbulence and/or bubbles in the water flow. Those things will reduce, distort or completely block the sonar signals depending on how bad they are. Steps are as bad as it gets - the worst possible case.

When you are on plane, those steps, and the bracket, are all completely out of the water. If the transducer isnt in the water, you have no sonar at all.

Even when going slow, the amount of turbulence and aeration from a step is far more than any other situation - like thru-hull fittings, strakes, etc.

One boats like yours, lots of guys add a second thru-hull or in-hull to get bottom readings when on plane. You wont see fish as very well with an in-hull though, but you will at least read bottom at higher speeds.

[Ted Martin]

Thanks Larry. I put the bracket at the bottom of the step, so with the drop the ducer itself sits just about even with the bottom of the pad.

if i am running, i just look at the gps, so not sure I will miss anything if it blanks out when i am going. If it don't work well, back to the drawing board i guess.





this old boat has been through a few generations of electronics now, evidenced by all the screws on her azz-end left behind from old ducers.

[Larry3215]

Hope that works for you.

[Ted Martin]

Hope that works for you.

me too.

the biggest thing i am concerned about is how it will come through the stump fields. amazingly i never had a problem with the old lowrance, once in a while it would get flipped up on the bracket but that was very rare. but that lowrance bracket had a notched gasket in there, so it was designed to flip rather than bend. I couldn't tell on this one whether the bracket would bend first or if it would just flip up; i didn't want to torque on it too hard by hand to find out.

[Todd Driscoll]

if i am running, i just look at the gps, so not sure I will miss anything if it blanks out when i am going. If it don't work well, back to the drawing board i guess.

Given that it seems not a big deal to you to not have depth readings at planing speeds, I would have mounted the GT40 up on or beside the jackplate since you fish lakes with a lot of stump hazards to get the xducer up out of harms way. Mounted up there, performance is still really good when you are idling, and it takes the stump damage out of play. Relative to your jackplate, if it doesn't have a holeshot/splashplate cover on the bottom, you may get some beam kickback interference from the inside of the jackplate when mounted higher as I suggest. This kickback will show up as 2-4 horizontal lines in the upper 10 feet of your Down/ClearVu display. Not a huge deal. Not sure if you will have any of this jackplate kickback where you have it currently mounted.

[Ted Martin]

Thanks for the input Todd! I appreciate it. See you are on Rayburn, there's a few stumps in that pond.