From my crank battery, I run a HDS 8 and LS1 on my console and it powers off whenever I start the big motor. There doesn't seem to be a problem with the battery, the motor cranks just fine and I keep it on a battery tender when the boat is out of the water.

Today, I used my aft livewell and whenever the areator turned on, the HDS would lose power.

Any ideas on what could be causing this drop in power to the HDS 8?

After the motor cranks or the livewell turns off does it come back on? What about when you tilt or trim?

It always comes back on, but has to go thru the power up process. If the motor is running, there is no problem with tilt, or livewell or any other power drain.....because with the motor running it is charging. But, if the motor is off, then even a small amount of pull from the battery, it makes the HDS start blinking and then eventually goes off, but immediately starts to power back up.

I don't think the battery power is low, because I never have a problem turning the motor over.

is it wired direct to the battery or through an accessory switch?
check the ground to the hds unit, loose ground will cause voltage drop when something else is powered up.
check fuse holder if its the round kind, make sure the fuse is getting good contact.
make sure the plug at the unit is in tight.
have your battery load tested, a fully charged battery will "look" good but may not have the amperage to push 3-4 things at once.

that is all I can think of at 0345.

The only way to track this down is to put a voltmeter on it. Then you can see if the battery is pulling down or if it's isolated to the console.

Check the battery voltage as it is cranking over. If it drops below 10 volts it will turn your graph off. Has said before load test the battery.

Also make sure your terminals on the battery are clean and tight. Loose or dirty connections will also cause this to happen.

Most likely a loose or corroded connection. Clean and reconnect, using dielectric grease.