Originally Posted by Richard B
True for car batteries, as you say. But don't use car batteries in a boat - use a leisure battery. They have thicker plates to withstand the internal stresses (which would buckle the plates in a car battery) created by longer cranking times and can handle deep discharge. (Ewwwww... that sounds unpleasant!!
Should have bought an Etec then, starts straight away
I think it depends on your usage TBH. I don't sit in the boat with stuff switched on and the engine not running, not for long anyway. As an added factor, and accepting this probably doesn't apply to anybody else on here, a car battery is what I can buy locally and anything else will cost a fortune as a special import. I also know that a decent heavy duty 4x4 battery will crank a diesel engine of the same cc as my Etec for quite a long time and in my LR I can probably leave the VHF on all night and get away with it so in the boat it's unlikely to be a problem.
If you regularly expect to significantly discharge the boat battery, or have lots of power hungry stuff on board, I'd probably agree with you. I don't - my charge/discharge pattern is pretty similar to a vehicle - so personally I wouldn't worry about it. When my Osprey's battery (which I guess probably is a leisure battery) is knackered, I'll just fit the biggest 4x4 battery I can fit in the battery box.
The flip side of leisure batteries is also that size for size their CCA is usually less.