Battery for a Big Twin?

What kind of battery do I need for my 40hp Big Twin? My motor has no generator and the battery will only be used for starting and occasionally for running lights at night. I spoke with my auto parts guy today and he gave me prices on "deep cycle" and "deep cycle/starting" batteries. I thought I could get away with just a basic car battery. Not true?

Re: Battery for a Big Twin?

Car batteries are designed to deliver high starting currents, and then to be recharged immediately. Their internal construction is also fragile, and may be damaged by a boat's motion. Marine deep cycle batteries are larger for the same cranking current, but will withstand being in a prolonged state of partial discharge, and will tolerate rough water slamming, and so on. The deep cycle / starting batteries are a reasonable compromise for many installations. It probably is a matter of relative price, and expected longevity.

Re: Battery for a Big Twin?

It doesn't take much to start your BigTwin. I have a 35hp Lark (1957) and have always used a standard car battery which works fine. I do keep a small solar charger on the battery as the pontoon remains in the water all summer. I very seldom have to manually charge it.

Re: Battery for a Big Twin?

I have used anything from large deep cycles down to small tractor batteries to start mine. The one I have now is the deep cycle/starting type. Let's put it this way: In 1963 there were not all of these options and car batteries were used.

Re: Battery for a Big Twin?

Thanks for the replies, guys. Out of curiosity, how much cranking would it take to drain a fully charged 550 or 650 CCA battery?

Re: Battery for a Big Twin?

I do not know about the CCA, but I'm in need of a new battery too and was thinking of just picking one up cheap at a "junk yard." I'm sure they would have a lot of very usable batteries. If the price is right, what's to lose?

Mas

Re: Battery for a Big Twin?

Don't want to burst anyones bubble but allow me to give you some information.

I work with the Coast Guard on vessel inspections (commercial shipping) and have been involved in numerous investigations into recreational vessel accidents/fires with the CG and Insurance company investigators. There is a growing trend within the insurance claim process where clams were denied and legal action taken against recreational boat owners that have used ANY type of automotive part, including batteries in a marine application.
Worked an accident last year where a boat caught on fire with injuries, when the investigation started it was found that an auto battery was the cause and the boat owner was brought up on charges and forced to pay the entire bill for injuries, LE and legal fees.

Just a word of warning in case you expect your insurance company to pay a claim! Marine parts are a bit more expensive but they are for a reason. They are designed for safety in a marine enviornment!

Boat Safe!

Larry