I put two of the blue top optima deep cycles (light gray case) in my boat to replace to wet cell group 27's. I run a 24V trolling motor, so it pulls from both and I crank off one and run my depth finders off the other.
The optimas were fine when I went to the lake to just boatride. But pull up to the beach and run the stereo for a couple hours or run the trolling motor for half an hour on a fishin hole and the optimas starting giving me problems. It would crank and idle fine, but when I hit the gas it would bog out of the hole and when it finally broke over it wouldn't run but 70 or 75. I'd run a couple miles and all the sudden it would take off and run like it was supposed to. I first thought I had a spark plug fouling out. Then had a mechanic check out my alternator. Finally started back-tracking and put a wet cell in and all my problems went away. Turns out that the computer on the newer motors (X, XS, etc.) monitor the voltage and put the motor into safe mode and limit you to 50% power if the voltage doesn't hit a certain threshold.
I also had a no-crank a couple times. The motor turned over just as hard as ever, but would not fire. I'd put jumper cables between the optimas and it still wouldn't start. But move the batt cables to the 2nd batt and it would fire right up.
I had to add a wet cell cranking batt to my setup, and that pretty much made the weight savings a wash.
An older motor with a computer that isn't quite as 'smart' might not have a problem with these batts. Optima also makes a blue top cranking batt (dark gray case) that would probably be okay, but it isn't made to be deep cycled so you wouldn't want to run a trolling motor off of it.
In my experience with the optimas, they drop voltage as the battery is discharged but have peak amperage output until they are completely dead, whereas a wet cell is the opposite (volts remain constant, amperage drops). After a day of fishing, the optimas show 50% charge remaining and still pull the TM just as strong as they did in the morning, but a volt meter will show less than 12 volts. My wet cells always showed 12.2-12.4 or something like that until they were almost dead as a hammer.
I even thought something was wrong with my optimas and swapped them for new ones at one point. The new pair responded the same way.
I like the way the optimas power my trolling motor, but the ones I have just wont work for a cranking batt. I've got an optima in my jeep too. THey are really good for something that needs continuous amp draw.
