Bad Battery or Starter?

Have the battery tested with a conductance battery tester.  Midtronics make them and all of the major auto parts stores like Advance Auto, AutoZone and Batteries Plus use them. Conductance battery testers measure the internal resistance of the battery and are very accurate finding failures like slow shorts and deteriorated and sulfated plates.  I assume you have checked for loose or corroded battery connections in the starter circuit.  

So I pulled the caps off the batter to look at water level and the plates.  The water level was somewhere between the top of the plates and the bottom of the hole.   I didn't look what "normal" was when I bought the battery.  However what caught my eye was a couple of tops of the plates didn't look right.   You can see in one picture the top of the plate has a shiny metal look.  The other picture has like a black coloring/swirl to it.  I don't know if that was the top of the plate or a buildup on the plate (sulfation?).  Whatever it is, I assume it's not normal or good.  

I am not 100% positive but if its like a car then stator should be powering the electronics for the engine. If that isn't working properly the power will be pulled from the battery killing it quicker so the next time you try and start the motor it will have less "juice"

also check the fuse on the alternator/charging circuit of the motor.

I don't know what kind of electronics you have but on the Gen 3 electronics you can put a voltage meter on your locator screen. I personally think you have a battery issue, Boat batteries get beat to death and I change all of mine every two or three years. Yes it is a extra expense but so is being stranded on a lake sometime.

Thanks for the input/thoughts.

Whenever I charge it, my charger says it starts out at around 70%.  When you say high rate of charge, do you mean how long does it take to charge it?   I do have other accessories tied into the battery, but use them very little.  I turn the electronics off when I get to a spot.  As far as checking the fluid levels, I haven't done that.   There was a time when the batter got knocked on its side and some fluid came out, but it looked like a small amount. 

I am leaning to towards battery myself since it always performs as it should after a good charge.  Just strange that it only takes a handful of starts, running the electronics a little where I start having problems.  Maybe the battery isn't getting recharged when I'm out on the lake running the motor, but should it really die that fast even if that's the case?  Maybe if that battery is that shot, that's all it takes.  

Battery

You mentioned charging your battery before each trip out, when doing so does it take a high rate of charge? You also stated it does this after fishing and moving several times, while fishing does your battery power any electronics or accessories such as live well, bilge pump or lights? If your electronics shut off once the problem starts it is a good sign the battery is bad. Most newer electronics are quite voltage sensitive and shut down if the proper voltage is not there. You can always take the battery out, charge it and have it tested at an auto service center or Fleet Farm if one is near you. Check connections at battery for clean and tight first. Then check fluid level of the battery.

if it starts eventually after either not engaging or spins slowly after engaging, could be a faulty starter/weak bendix 

lots on youtube to checkout starter

www.google.com/search

Sounds like a battery to me. Also if you have a meter that reads the voltage output when the motor is running it should be above 12. If it is not you might want to have your stator looked at. That means your battery isn't being charged while the motor is running.