My trolling moter is 36 volts. I'm running 4 batteries. Can I drop a battery and hook up my depth finder and cranking cables to one of the batteries and be at 12 volts. I'm thinking I can just want some input

No you can't. You can run the electronics on the deep cycle batteries, but not the engine. Regardless of what anyone says, you can't do this and get by. You'll pay for it if you try it.

I dropped my 36 volt motor and opted for three batteries. With todays motors,24 volt ones are strong enough.

What will it do?

this is what I want to do. It's a 19ft blazer. Think it has a 108 moterguide. I'm wanting to go to a 24 volt fortrexx. Just not in the budget at this moment.

Cause real bad interference on your electronics, draw down your battery probably always have cranking issues not enough juice., Just a bad idea.

I've always ran everything of cranking battery, never had any problems. Yes, that trolling motor will work on 24v.

All my electronics are run on the cranking battery. Never had any issues

You electronics will have interference, they'll remind you of white noise on a tv. The engine isnt designed to run on a deep cycle battery. A cranking battery is designed to put out a whole lot of amperage at one time, where as a deep cycle battery is designed to put out a little but over a long time. It will eventually burn the starter up, and kill the life of the battery leaving you stranded.

I am not real sure about the science behind some of that.

why?

Why do you say an engine is designed to run on a deep cycle battery? Just how will using a deep cycle battery kill a starter? A deep cycle battery is designed to be run down to a low voltage and charged back up without hurting the battery. You can't do that a lot with a cranking battery. A hot battery is all that matters to a starter. I have never had any trouble running a deep cycle in a boat as a cranking battery. I can see getting some interference on the electronics but a ferrite coil will fix that.

well first of all I made a typo, go back and look at my post. I corrected it. Second of all, a deep cycle battery will not put enough amps to the starter that is required at one single time. This will wear the brushes out in the starter. How long will it take, that's the question. It may take a long time on a 1992 Johnson GT150, but won't take very long on a Yamaha HPDI, or a Mercury Pro XS. TCI ignition is different than CDI ignition. A 3/4 charged deep cycle battery won't even crank a TCI ignition motor most of the time because it won't spin the motor over fast enough to turn the ignition on, especially once you've been fishing all day and ran that deep cycle battery down.

I have a ProXS 225 and it needs a lot of amps to turn that motor over.I run a 31 series AGM battery the 27 and 29 batteries barley meet the min requirements and it didn't take much draw from the adcs and electronics to put a strain when cranking, and put a cold morning and then your in more trouble. My 31 AGM is plenty on battery with lots of reserve.

You can't meet the required cca's with a deep cycle battery

how do you like that proxs? Which year model? I work for Yamaha but I have to say I've always liked a proxs. Good strong motors. I cut my teeth when I start learning to be a mechanic on mercurys.

I'm on my 3rd Pro XS and I love them. Never had any major problems. They use very little gas and oil also in my opinion. We will let WIDGEON give his thoughts but great motors in my book

Its a 2011, I wanted a Skeeter but they only had the Sho and in 2011 they was has issues with them and I stayed away. I ve had 2 ProXS they are solid engines fast plenty of power and easy on gas.. However today 4 strokes are solid engines with plenty of torque and can run with 2 strokes. My next engine will be a SHO since they have all the kinks worked out.

Yea the SHOs were fixed in 2012. all powerheads were warranted in or out of warranty when they failed. The powerhead was the only problem then. Lots of people ran them until they popped, had the powerhead replaced and then were good to go. The SHO was the most radical thing yamaha had done up to that point. The testing was done extensively, but the bad batch of parts was the only mistake.

2009 is when the Pro XS started getting pretty solid, from then on out they're hard to beat.

The SHO has better hole shot than the Pro XS and the HPDI, better mid range acceleration, but the top end are pretty close to each other. The Pro XS is a fast motor top end. But the kicker to it is, the SHO will outrun it out of the hole and in the mid range so the Pro XS has a hard time catching it by that point. We sold about equal amounts of each engine when I was at the dealership. It really came down to which one we had more of at the time. Customers loved both engines quite a bit. If I were to buy a new one now, it would be either of those.