Marine/RV Starting/Deep Cycle Battery for engine starting

It depends on just how "deep cycle"" is the multipurpose battery, what is its output when temperature drops to -20 F, and how hard your engine is to crank and start when it is that cold.

I would have no problems being lightweight on cranking power in Florida, or anywhere on the West Coast where "cold" is just somewhere around freezing, but for winter in Montana or Alberta I would want a starting battery with the highest CCA that will fit in the battery box.

Thanks for all the replies. Cold cranking amps for the Kirkland Signature (Costco) marine battery 27DC is rated at 600 A @ 0 degrees F and 750 A @ 32 degrees F. I see that this rating is comparable with the "starting batteries" that they sell. I'm going to try it.

It will work, but a deep cycle battery won't have as many cold cranking amps, as a starting battery. Maybe not a problem if you not using it in extreem cold weather.

VE3ESN wrote:
It's the primary starting battery I'm replacing. Can't find a group 27 starting battery at a reasonable price so am hopeful that a Costco dual-purpose marine/RV "deep cycle" will serve as the engine starting battery.

It will work just fine.

I don't know where in Ontario you live but our Costco in Toronto has them. Saw it there last week.

JMO Die Hard batteries from Sears are still one of the best chassis batteries made. I like the Die Hard Gold, not cheap, but a very good battery, with a good warranty. They are often on sale, or if not, if you ask they will usually give you the sales price.
You want a "Group" starting battery that fits your Dodge, not a group 27 deep cycle battery.
Here are a few different choices for car batteries.

http://www.consumersearch.com/car-batteries

Marine batteries are DESIGNED for starting engines and deep cycle is designed for repeated charge/discharge cycles. Since you are talking about a combination starting and deep cycle battery you can expect that it will do NEITHER of these functions as well as a specialized battery but will do BOTH of them well enough to do the job. Probably will just not do them as LONG as specialized batteries.

It's the primary starting battery I'm replacing. Can't find a group 27 starting battery at a reasonable price so am hopeful that a Costco dual-purpose marine/RV "deep cycle" will serve as the engine starting battery.

Most Roadtreks come standard with a group 27 dual purpose battery. The Costco Group 27 DP battery will work just fine, be sure to properly secure the battery so it doesn't move after replacing it.

Although I should ask are you replacing the primary starting battery or the axillary? I would assume the axillary battery since you said it was the Group 27.

I have used these group 27's Marine Deep cycle/starting for over 15 years . No problems .