Humminbird Helix 9 SI Mega + won't read depth on plane – need help

I recently had a Humminbird Helix 9 Mega SI+ GN3 installed on my 2013 Tracker Targa V-18. It works great but I cannot read depth over 15 mph. I have heard that this is common and I may need to add a 2D transducer and Y-cable but I am wondering if anyone has the same unit/transducer and can get it to read depth on plane? I tried some minor adjustments with no luck so far but haven’t decided yet if I should install the additional transducer or try more adjustments first.

It is most likely coming out of the water and the transducer needs to be adjusted lower

mojogunter wrote:

It is most likely coming out of the water and the transducer needs to be adjusted lower

I agree. I currently run a Helix 9 G3 mega SI and had the same problem. I lowered the SI transducer to an 1/8” below the hull and now it reads at faster speeds. The guys here just helped me with some guidance on this about a month ago.

The best thing you can do is get the y cable and add the 2d high speed transducer. The mega si is an expensive transducer and should be mounted above the bottom of the boat, it is not really designed to pop up if it is struck. I’ve done this on my last two boats and couldn’t be happier. With the splitter cable the unit automatically switches to the transducer that is needed when you change views.

I actually added an additional splitter to separate my si to individual transducers to correct the motor from causing interference.

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It’s as low as I can get it without drilling new holes. Still needs to go lower?

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It’s hard to see from that angle. I would take a straight edge and hold it on the face of the transducer to see where it’s positioned in relation to the hull. If it needs to go down a little, you may be able to quickly file or dremel the slots to get a bit more room vs. new holes, though I do see you have a mounting plate, so new holes don’t mean drilling into your boat.

Try her out

I had mine that low and I think it was creating a bubble. I moved it up to sit just barely below the bottom of the boat and now it works at all speeds.

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Thanks everyone. I added the Y cable and high speed transducer. In the process I moved my SI transducer up quite a bit (where the instruction sheet says to) and now I even get SI at speed. So o guess I really didn’t need the extra Y-cable & HS transducer (or extra $125). I should have just been more patient and adjusted the height of the SI transducer. I had a boat dealer install it so I figured they would install correctly but I guess not since it needed to be move up even beyond where the screws were.

I have the same issue as the depth reads correctly then flashes to 3 feet or any number then back. I have a shoot through hull. I had it explained to me my keel guard could be the cause because it is breaking up the flow of water that the transducer is reading. Anyone ever hear of this? Everything works great when not on step.