No one is saying that your batteries won't work. We're simply saying that it's really not necessary to go with batteries that are that expensive. It's a fact that deep cycle batteries cost more than regular lead/acid and really don't deliver any added value for normal usage. :head:

Every engine manufacture states in their installation guide specifically to NOT use deep cycle batteries as a starting battery. Deep cycle batteries are for trolling motors and battery banks. A starting battery will run all your electronics and them some. Using a deep cycle battery for electronics comes from the car stereo guys(oddly enough, they will do better with a starting than DC) and has no merit. I sell quite a few batteries each year and can tell you, all batteries are not the same. The Deka 24M7 is probably the best battery out there right now. You can use a deep cycle battery to start an engine, buts its not the best battery to use. Use of an incorrect battery can effect your engines warranty as well. Mercury has gotten very specific about it with their outboards

Mercury has to blame it on something....:nut:
**************************************

I think the key to this argument is the application of the battery.
I think most V20s are run during daylight and have minimal draw on the battery for short periods before running and thus recharging.In this application, a starting battery will be fine.

I used to drift or anchor for hours, often at night. I used to turn on my floods and underwater light at the dock and fish for stripers under the dock. It wouldn't get charged until the next time I ran it. I used a single 27DP for 18 years and it worked great.

As for a DC, they are for House batteries on large boats with multiple banks or for electric trolling motors.


Here is West Marine's take on battery selection.

Starting batteries

Starting batteries, which crank the starter of your boat's engine, are the sprinters of your electrical system. They deliver between 75 and 400 amperes for 5-15 seconds, and then are recharged in short order by your engine's alternator. Like all lead-acid batteries, they are constructed with alternating layers of negative and positive plates with insulation between them.

Starting batteries have thinner and more numerous plates, providing extra surface area to generate high amperage bursts of current. The two drawbacks of this construction are that the plates are relatively fragile in high-impact environments, and that starting batteries do not tolerate deep discharges, which reduce their operating lifespan.

Deep cycle batteries

Your boat's house battery bank uses deep cycle batteries, the marathon runners of the storage system. They power the electrical loads on your boat when no charge source (shore power charger, engine alternator, wind generator or solar panel) is available. Consider them a kind of savings account into which energy is deposited or withdrawn.

Compared to starting batteries, which deliver high bursts of energy for short periods, deep cycle batteries recover fully after being heavily discharged over longer periods because their design features thicker plates with a high content of antimony. Overnight, their use might deplete 50-70 percent of the battery capacity, depending on the house loads of the boat. When the batteries are recharged, energy is re-deposited into the bank, and the process, or cycle, starts over. Generally, deep cycle batteries should be sized to store three to four times the expected amount of energy to be used between recharge cycles.


Dual-purpose batteries

We generally advise that you choose either a deep cycle or starting battery for best performance and battery life, but dual-purpose batteries work well in some applications. With large, thick plates containing more antimony than starting batteries and an active lead paste chemistry, dual-purpose batteries are a good compromise, tolerating deep discharges that would ruin a typical starting battery. Since they have lower storage capacity than comparably-sized deep cycles, we recommend them for the following applications:

Runabouts or other small powerboats using a single battery for both starting and running loads with the engine turned off.
Sailboats with two identical batteries used interchangeably for starting and house electrical loads.
Boats with one battery bank that does double-duty for house applications and engine starting. Dual-purpose batteries will last longer and give more reliable service than a starting battery, for about $20 more per battery.

It would to be great to have a Agm starting battery and 2 DC house batteries, but where to put them?
I use 2 group 27dc delays, I power alot of equipment, more than alot of bigger boats.
I would not be suprised to see merc require a Agm for starting, alot of cars do.

I was just stating that a DC battery will work fine for starting 90% of the outboards out there. Most do not require over 450amps to start, even a centennial battery might do that...maybe.

if its got a computer on the engine, the manufacture its most likely requiring at least 850 CCA. Mercury requires more on their Verado's. Unfortunately, the only thing available to meet Mercs spec that will fit in the box is AGM batteries, I throw those POS in the pile all the time, especially the optimas. 30 years working on boats, very hard to beat a Deka 24M7 starting battery. BTW, you cant mix AGM batteries and wet cell if they are charged by the same source.

You can IF you properly isolate the batteries from each other. RV's routinely use lead acid batteries for starting and agm for the house loads. They install an isolator so the alternator charges each battery bank individually off of 1 alternator. Or you can run a dc to dc charger or charging relay setup to also do it. You just have to use a system so different battery types are not paralleled at rest because agm batteries have a higher static voltage than lead acid do, so if you mix them, the lead/acid will constantly drain the agm battery at rest.

Correct, AGM and lead acid charge differently, that is why most AGM batteries die early.

I have had no computer issues with my Evinrude and the computers in 10 seasons with all the computers on her.

Just my experience and opinion, if you gave me a Merc verado....i would not take it.