I am wrapping up the initial rigging on my wife's Hobie, but I have a small issue. When the fish finder is on, the LED's flicker slightly. It's a continuous, rhythmic flicker and I am assuming it's being caused by the power drop when the sonar pulses. It still does it when I turn one set of lights off. Is the 17.5Ah battery too small? Components are listed below.

FPV Power 17.5Ah 12V Battery
FPV Power 3A Fused Cable
FPV Power Splitter Cable

Splitter Side 1
FPV Power 1.5A Voltage Regulator
Lowrance HOOK Reveal 9" TripleShot (1.5A Draw)

Splitter Side 2
Yak-Power 8-Channel Switching Hub
(2) 10" LED Strips - NAV Lights
(2) LED Button Lights - Red
(2) LED Button Lights - White

I pulled the voltage regulator and ran power direct to fishfinder. No change other than the power to the fishfinder dropped from 12V to 11.8V. No change in volts when all lights were turned off.

I hate wiring. I've typed a response and deleted it about 6 times so far. For some reason I keep coming back to possible interference from the fish finder/transducer, as I believe you have plenty of power. You could double check this by connecting a separate battery to the lights and seeing if the fish finder being on still causes the flicker. If so, there's some sort of interference. If not, then there's a wiring/power issue. Are the transducer wire and power wire ran in close proximity to each other?

I ran them as far apart as possible, on opposite sides of the hull but between the foam blocks. But now that I am typing this, I did just remember, the bundles of extra transducer wire and extra power wire are both laying in the hull directly above the transducer. I will check that, then the separate battery trick you mentioned. Thanks for the help.

No way to be sure without hands-on testing, but I'm guessing a poor ground or a poor hot connection. Gotta get in there and dig. Check all connections; make sure they are clean and tight. Use dielectric grease to seal them. Assuming that your battery's good, you have more than enough amperage.

Plenty of power. It’s not a power issue…..unless it’s a bad battery, but you are not describing a bad battery.
Agree that it is some sort of interference, or possibly a poorly insulated connection.

Move the wiring and secure it.
Check the connections. Go ahead and add extra liquid electrical tape if the connections are good.
They sell Ferrite wire clips to reduce interference. They are not expensive. Available in multiple sizes.

…LED lights will rarely/never be used unless lots of night fishing.

I am not an electronic guy so take this with a grain of salt, but I can't help but wonder if the 3a fuse has something to do with it (might be defective). If it was me, I would spend a few minutes isolating this before tackling other potential issues.

Saying this, I tend to agree that it's most likely some sort of interference from the transducer. Your transducer is powerful (i.e.: sidescan / downscan) and LEDs can be finicky... there are a lot of micro components in an LED strip. If you have a spare battery at your disposal, you can temporarily wire the lights to a separate battery. If you still have the same problem, then you know 100% that the problem is ambient interference vs wired interference. If ambient, all you can do is separate and insulate. If wired, follow Jim's guidance.

Good luck!

just to add a little experience also.......and I am no electronic expert either. I had a garmin unit that I could not get rid of two different types of interference, one when the trolling motor was on and the other while less severe just seemed like unnecessary screen noise that would come and go.
I did everything any you tube vid said including reroute wires away from everything else, changing grounds adding shielding, installing stand alone battery to run the sonar, cleaning connector pins. nothing helped until I installed these ferritic choke clips noted above. I cant explain it but we are all very happy now.......and of course your mileage may vary

Thanks for reporting back, this is good intel to know.

CCTX for the win