After some research on the internet, finally found a way to flash my GPSMAP 86i by using updater.exe successfully.
for a force update using updater.exe on my GPSMAP 86i
step1: Disconnect GPS form computer
step2:
Drag and drop the patched .rgn file to the updater.exe, windows should appear and the USB Device column should show gray color with no device attached, choose it.
step3: Connect the device to PC with USB cable and immediately
press and hold the D-PAD (Up) button after GPS power on.(this will force the GPS go into the
Mass Storage Mode)
step4: The device will show up in the USB Device column,
keep holding the (Up) button , click OK to begin flash.
step5: When the GPS unit displays "Software Loading", release the D-PAD (Up) button.
step6: The Updater will display a download progress bar, When the flash is complete, the updater will display a 'Successful Update' message.
step7: The GPS unit will restart with the new firmware version installed.
Enjoy the unlocked device.
the original tutorial links here:
[Please Register or Login to download file]