My trolling motor battery seems that it isn't lasting as long as it used to.    Anyone know of any tips to prolong its charge or do I just need to buy a new battery?  Does it harm a battery to be partially discharged and recharged often or would it be better to fully discharge it before recharging it again?  Is it alright to leave it on the charger continuously (it's an automatic charger).

Will it harm a deep cycle battery to recharge it off a car engine with jumper cables?  They are both 12V systems, but I understand there is a difference in the type of charge a car produces vice a slow electric trickle charger.

When buying a new battery, are the deep cycle marine batteries worth the cost to use on just a trolling motor or will a regular auto battery work just as well?

Lots of questions here I know, but any advice would be appreciated.

Thanks in advance.

Yes, you need a deep cycle. Check this out..............Al

http://www.marine-electronics.net/techarticle/battery_faq/b_faq.htm#3

My trolling motor battery seems that it isn't lasting as long as it used to. Anyone know of any tips to prolong its charge or do I just need to buy a new battery?

The best way to do this is to make sure it is fully charged before you use it.

Does it harm a battery to be partially discharged and recharged often or would it be better to fully discharge it before recharging it again?

Deep cycle batteries are not made to be fully discharged. They need to be used and then charged back up within 24 hours.

Is it alright to leave it on the charger continuously (it's an automatic charger).

Some do, I don't because it will cause the water to evaporate more quickly.

Will it harm a deep cycle battery to recharge it off a car engine with jumper cables?

It won't harm it but you can't get a full charge with jumper cables.

When buying a new battery, are the deep cycle marine batteries worth the cost to use on just a trolling motor or will a regular auto battery work just as well?

Yes they are.  Regular cranking batteries are not designed to operate trolling motors.  They are designed to give you a quick output to start an engine not give a low draw over time.