Help, Depth Finder shuts down, when starting motor

I have a custom made boat, River Wild. When I ordered the boat I want dual batteries, up front..for weight distribution.

The problem from the "get go", if I start the motor either my ETech 105 or my Yamaha 8 and the depth finder is on....motor starts but depth finder goes blank.

I had 2 marine batteries, size 24, just replaced the 24's with 2 marine size 31. I thought the bigger batteries would eliminate the problem...
played in the Chehalis today....same problem.

I have gotten good at re-starting the depth finder but would prefer not to have to do that....

Looking for a possible solution?????


Oh, I do have a perko switch, doesn't matter if on 1, 2, or All

Since I am chasing (so far unsuccessfully) my own 12V gremlin I won't offer any suggestions on what may be causing the problem. However, until you can sort it out you might want to consider a battery solely for the depth finder and recharge as necessary at home.

Is this a starter switch issue? That is the finder is wired into the starter switch and therefore it is disconnected from battery every time you cycle the key? You might try as a test, to wire your finder directly to the battery - see if that solves it. Many starter switches kill power as you cycle from off to start, back to on.

Kyle_A:

Now that sounds like the problem.....boat builder put the Perko switch in the most terrible place to try to work on but for $$$$, bet I can find a marine shop to "help me out".

Thanks

I have had this problem and seen it on other boats as well. When the dealer did the FF install they wired the 12v lead into the ignition circuit behind the dash. They spliced in to the hot lead and it would cut out every time the motor fired and cause the FF to shut off then turn back on.

My solution was to just pull the FF hot lead from the ignition wiring entirely and wire it to its own dedicated, fused circuit. Problem solved.

First thing I'd do is get a multi meter from Harbor Freight. An acceptable digital is less than $7. Put it on the power terminals on the plug that goes to the depth finder and see what the voltage reads with the main in off, start and run. Off 12.6, Start 11.6, run 14 would be expected.

Some finders are oversensitive to battery voltage and do a shut down when no one else cares. I have a Fusion radio and an old Lowrance HDS that occasionally do the same thing. Never when starting my T8 though.

Lowrance HDS Gen 2 Touch spec is 10.8 to 17 vdc. which should allow it to continue running during a motor starting draw down. I personally do not trust the 10.8 bit.

Usually FF are voltage sensitive as stated by Slow Boat, meaning a drop or spike can cause them to shut down. Lots of issues can cause either situation. Not knowing your boat if you keep that in mind while troubleshooting it may help to isolate the problem. If not experienced in troubleshooting DC, your best bet is get it to someone who is.

Thanks for the help...I'll give one of the above a try.....


Good luck on the fall salmon season...………..

I say sink the damn thing and start over....

get a new depth finder

Thanks for the extra comments...….lol

Still, have a good fall season......Humptulips for Chinook, and other GH rivers for Coho.....

Similar to what others have said... it's a voltage drop because your batteries are up front. Lowrance are the most finicky i've seen for this.

If you make sure you have good clean power to the fish finder, the only other options (besides getting a different FF) are to put the batteries in back or run very large 1/0 or 2/0 battery cables from the batteries to the motor. It's usually the voltage drop on the batteries from starting the motor.... not poor power to the FF.

Sounds like the culprit! Length of wire and wire size, also copper vs aluminum. Ohm's law applies here. Use bigger wire and copper to help that voltage drop.

Yep... I'm 99.9% confident that's it. Because I've dealt with it on the last 2 sleds after months and months of troubleshooting and racking my brain.

Right now I have 17' of 2/0 battery cable running from the batteries to a post in the rear. Overkill... not for a modern DI 2 stroke. Everything else... slightly overkill.

Drifter, what size wires you got running from the batteries to stern? 4 gauge? Does your etec run really rough at idle and low rpms?

mitch184:

Bingo.....I know you are correct.....boat was custom built, person knows how to build boats.....not so much with the wires that run from stern to batteries in front.

I was told the cable were not the correct sizing but would have to tear up the floor and replace with 2/0 cable.....I think this is the problem but time and $$$$$$$ invested just doesn't seem to offset the "re-starting" the fish finder...

ETech runs awesome from idle to 5100-5200 RPM, at 39-40 mph....The 150/105 ETech is one heck of a motor, 2 stroke factory installed pump so runs better all the way thru the RPM range.

Will leave it this way, until summer 2020.....then maybe the 2/0 cables.