Lowrance Hook Reveal Black Screen: Step-by-Step Fix

Cause 1: Corrupted SD Chart Card

The Lowrance Hook Reveal checks connected SD cards during the boot sequence. A corrupted Navionics or C-MAP card causes the unit to hang before the display initializes — producing a black screen that looks like hardware failure. This is the most common cause and the easiest to rule out.

1. Remove all SD cards from both card slots (Hook Reveal has one on the front face, some models have a second on the side or rear).
2. Power cycle the unit — full off for 30 seconds, then back on.
3. If the unit boots without cards: reinsert cards one at a time to identify the corrupted one.
4. If the bad card is identified: reformat it (FAT32) on a PC, then re-download your chart data from the Navionics/C-MAP app to the card.

Cause 2: Insufficient Supply Voltage

The Hook Reveal requires a minimum of 10.5V at the unit's connector to boot reliably. Corroded battery terminals, undersized wire runs, or a failing battery can cause the unit to brown out during boot — the processor starts but the backlight or display driver never gets enough power to initialize, producing a black screen.

1. Measure voltage at the unit's power connector with a multimeter, not at the battery. Key-on, before and during boot attempt.
2. A fully charged 12V system should read 12.5–13.5V. Below 12.0V indicates a battery issue; below 10.5V and the unit won't boot.
3. Check the power wire gauge — a long run with undersized wire creates a voltage drop. Lowrance recommends 14 AWG minimum for runs over 10 feet.
4. Inspect the ring terminals and fuse holder for green corrosion. Corroded connections create resistance that drops voltage under load.

Cause 3: Firmware Hang

Firmware hangs can leave the unit in a state where the display never initializes even though the processor is running. A short press of the power button does nothing because the firmware isn't responding to input.

1. Hold the power button for 15–20 seconds — this forces a hardware-level power cutoff on all Hook Reveal models.
2. Wait 30 seconds, then power on normally.
3. If unit boots: update the firmware via the Lowrance Software Update and Network Tool (LSUNT) or via SD card from Lowrance's website.

Nuclear Option: Firmware Reflash via USB

If none of the above work and the unit shows no sign of life despite confirmed good voltage, the firmware can be reflashed using Lowrance's LSUNT software on a Windows PC connected via USB (required — Mac is not supported for this procedure).

1. Download Lowrance LSUNT from the Lowrance support site.
2. Connect the Hook Reveal to your PC via the unit's USB port (rear of unit, requires a USB-A to micro-USB cable).
3. Hold power + Menu simultaneously while connecting power — this puts the unit in update mode.
4. LSUNT should detect the unit and allow a full firmware reinstall.

Parts reference

Part	Typical cost	Notes
Navionics+ SD chart card	$100–130/yr subscription	Most common chart card for Hook Reveal. Annual subscription model.
Lowrance power cable (replacement)	$18–30	OEM part; also available as aftermarket with integrated fuse holder.
Inline fuse holder + 3A fuse	$6–12	If original fuse holder is corroded, replace rather than just the fuse.