You can run a Marine Battery in your vehicle. What you want is a Marine Starting Battery, Not a Deep Cycle Battery. Just match the CCA required for your vehicle. A Deep Cycle battery is designed for RV's on the battery side and for marine applications such as trolling motors. A starting battery is similar to an automotive battery. I use Marine Starting Batteries in my run abouts simply because like you, they are cheaper. I normally install a 650 CCA battery and purchase mine from Academy Sporting Goods which is way cheaper than buying one at Walmart or other retailers.

You can if it fits. Honda batteries are generally very small and you may not be able to find the right shape.

Will it start the Honda? Kinda important that the car get started.

The marine batteries are usally much more expensive (per CCA/AH)...

Your motorboat battery is (should) be a 'deep cycle battery' - otherwise saying, it can get very low on power and not harm the battery, unlike a car battery. When a regular car battery dies/runs too low, it damages the battery, shortening it's life.

So, back to your question - YES, you can! As long as it is a 12v battery and is the same amperage, or at least close in amps {cold cranking amps} or 'cca' then it will work. It may or not FIT, but that's another story.

If the amp capacity of the boat battery is as high as the OE in the car you can.

Can you use a motor boat battery for a car since, those are twice as cheap for a smaller car like honda civic, as far as I know the car gets all its energy when running from alternator.