Possible Electrical issue

[redac7]

I'm seeing the following symptoms when I'm running my 2005 Mastercraft X10 where if I'm doing something like driving down the lake and pumping water in/out ballast tanks with the radio running then the depth finder starts blinking and acting like it is not working. It seems like when I have the boat running with ballast pumps running, radio, depth finder etc there is not enough power. I have the standard amp and no additional speakers other than the subwoofer, 4 internal and 2 tower speakers. I do only have one marine battery and not a dual battery setup but I still feel this should be enough power from the running engine and battery. From this I have the following questions:

Could there be a ground somewhere?

Could the battery be going bad?

Could the alternator be going bad?

Could there be some weak connections where I need to apply dielectric grease?

Thanks for reading and for the help!

[Tsumi]

What does your voltage read when this is happening?

[skydyvyr]

Um, the depth finder on my boat (built in to my multifunction medallion Speedo) always flashes when I’m underway. I assume that the turbulence of the water passing under the boat interferes with it’s ability to send and receive an its ping. If your depth finder is different than mine, the behavior you mention could be electrical.

If so, it could be any of the reasons you listed above. Tsumi is right to ask what your voltage is. If it were my boat, I would check things in this order:
1. Check the battery. How old is it? Has it ever run dead? Does it read 12v with nothing connected to it? 12v at an idle battery doesn’t guarantee it’s a good battery, but not having 12v would indicate a bad battery (assuming it is has taken full charge). In reality, if the battery is cranking and starting the engine reliably, it is unlikely that it’s the problem, but I’d start here because it is the easiest to check.
2. Check for corroded or loose electrical connections. Start with batt terminals bus bars and circuit breakers, particularly any locations where multiple wires are joined in a single connection. If there is an inline fuse holder for your depth finder (assuming it’s aftermarket). Corrosion on a connection or wire increases resistance to voltage, which reduces the voltage available to devices at the end of the line.
3. Get the alternator checked. Honestly, I doubt this is the problem because it it was failing, you’d have a whole host of other issues going on, not the least of which would be a dead battery after a day on the lake. If the alternator was failing, and not producing enough power to run your accessories, then they would draw power from your battery until it was dead, and at that point your motor would also stop running (no spark, no ECU, etc.). If everything else is ruled out, this could be your issue, but based on your description, I think it’s highly unlikely.

At the end of the day, if the problem is indeed electrical, I’d guess that the issue is in the power line to the depth finder, then possibly a weak battery.

Hope this helps
—Sky

[redac7]

Thanks Tsumi and Sky for the the help! I will check the battery voltage when I get the boat back out on the boat but in the meantime take it to a shop to get it tested.

The depth finder will flash when I'm underway I would say less than 10% of the time but when I've got all 3 ballast pumps running pumping water in/out it with flash most of the time.

[LDA6339]

Thanks Tsumi and Sky for the the help! I will check the battery voltage when I get the boat back out on the boat but in the meantime take it to a shop to get it tested.

The depth finder will flash when I'm underway I would say less than 10% of the time but when I've got all 3 ballast pumps running pumping water in/out it with flash most of the time.

Could be the flow over the sending unit being disrupted by the pumps? Would be weird but I suppose its possible.