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Author Topic:   do I need a deep cycle battery?
wriling posted 07-29-2004 07:33 AM ET (US)   Profile for wriling   Send Email to wriling  
Hello all,

I originally posted this in the general forum but realized that it should be posted here.

Anyhow, the battery in my 1986 Montauk needs to be replaced and I could use some advice on a new battery.

The current battery is a deep cycle and I am wondering if I should continue with a deep cycle battery as I was told it should never be used to start your outboard.

The Montauk is a one battery set up to start a 90 HP Evinrude VRO ('86, rebuilt this year). The battery also runs the VHF, fishfinder, lights, GPS and 12V accessory socket.

Any advise, as always, will be greatly appreciated.I am mechanically challenged to say the least.

Thanks again,

HAPPYJIM posted 07-29-2004 07:38 AM ET (US)     Profile for HAPPYJIM  Send Email to HAPPYJIM     
Just a regular group 24 battery will do. I get mine from Wal-mart, $40 and free exchange for 3 years if it fails.
wriling posted 07-29-2004 08:08 AM ET (US)     Profile for wriling  Send Email to wriling     
What should the amps be? Also, what is the differnce between a deep cycle and a regular? I have so much to learn.


diamondjj posted 07-29-2004 09:12 AM ET (US)     Profile for diamondjj    
Wendy, Check out the following. It should answer all your questions. Basically, deep cycle batteries have heavier plates
inside the battery and are commonly used in sailboats where batteries are discharged and charged frequently. The site below explains it in more detail. I have deep cycle batteries on my Whaler... a carry over from my sailing days.
gnr posted 07-29-2004 10:31 AM ET (US)     Profile for gnr  Send Email to gnr     
If you often use accessories that run off the battery while the engine is not charging the battery you should consider the deep cycle.

A regular battery is not made to be drawn down and recharged frequently like a deep cycle is.

I run deep cycles on my boat also.

wriling posted 07-29-2004 12:38 PM ET (US)     Profile for wriling  Send Email to wriling     
I checked out battery faq and I can honestly tell you that it all looks like rocket science to me (my mind has a real attitude problem when it comes to math & mechanical understanding).

I was given a marine battery this morning by a fellow worker, it's not a deep cycle, and I was thinking of trying it out. He thought it would be adequate.

Because I had lost battery power on the deep cycle last week (at the most inconvenient time, of course) I have since purchased a portable jump box which I will not carry with me on the boat.

Thanks for the advice so far, I am open to any!


HAPPYJIM posted 07-29-2004 12:54 PM ET (US)     Profile for HAPPYJIM  Send Email to HAPPYJIM     

If the battery that was given to you is new,that's great.
If it is used, charge it fully then take it to a service station to do a capacity check. They will place a heavy electrical load on it to test. If it works good install it. If the test fails, spring for a new battery. The only thing worse than a dead battery on the water is running out of gas.

wriling posted 07-29-2004 01:23 PM ET (US)     Profile for wriling  Send Email to wriling     
Happy Jim,

The mechanic at my job did do a load test and he said the battery was very good. I don't really have a problem springing for a new battery, they are actually quite inexpensive. I just hate having to drag my butt to to Walmart (I dislike shopping so much I buy everything online).

Again, I just want to make sure that I have a battery capable of starting the engine, as well as running the accessories. When I lost my battery power last week I was out on the water, thankfully a boater came by with some jumper cables. Thats why I intend to keep a jump box on the boat, just in case.

I was told that I deep cycle battery should only be used to start an engine in an emergency.

Buy, there's alot more to owning the Montauk that my little 13 footer.


JohnJ80 posted 07-29-2004 02:22 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
Deep cycle batteries are not designed to be starting batteries.

You should have a standard cranking/starting battery for your starter.

If you add a lot of accessories, then it is a great idea to also have a deep cycle battery on board.

On my boat, I have a cranking battery for the motor alone. Then I have a deep cycle that runs all the accessories, trolling motor and lights. I have a thing that allows me to charge both batteries (separately - the deep cycle charges after the cranking battery comes to 13V).

If there is a problem with the cranking battery, I can always use the deep cycle to start the engine.

This setup gives a fair degree of reduncancy - always a good thing in a marine evironment.


BW23 posted 07-29-2004 03:09 PM ET (US)     Profile for BW23  Send Email to BW23     
Deep cycles, size 27 start my MERC 225 EFI just fine.

I'm staying w/ DC's for my style of boating/fishing.

davej14 posted 07-29-2004 07:17 PM ET (US)     Profile for davej14  Send Email to davej14     

I just replaced a battery and did some research before the new purchase. I concluded that it was most important to purchase an "AGM" type battery which stands for "absorbed Glass Mat". They come in starting and deep cycle versions and are a bit more costly ($80 to $120). The important things about this type of battery are that it is very resistant to shock and vibration, can go long dormant periods without losing its charge, it is totally sealed so it will not require you to check the electrolyte level and it will not produce corrosive fumes in your center console. Unless you use the battery to power accessories for LONG periods without the motor running then you should go with a starting battery. It seems to me a logical choice given the accessories you mention. For example a car battery is a "starting" type battery.

Another point is that you are located in a cold winter environment. The lower rate at which an AGM type of battery discharges while not in use would allow you to leave it in the boat over the winter without having to worry about it freezing and it should be ready to go in the spring without a charge.

Always purchase a battery with the minimum CCA (cold cranking amp) rating specified by your motor manual.

My last comment is that most shops do not know how to test a battery properly. Even the load test done at local car shop is just an indicator and will not show the actual capacity or condition of a battery. Some chemical changes of the battery electrodes are irreversable and not easily detected after a full charge. The bottom line here is that if your battery died on you during normal use AND there is no logical explaination like electrolyte level being low, lights or accessories were left on etc, then I would replace it.

wriling posted 07-29-2004 08:23 PM ET (US)     Profile for wriling  Send Email to wriling     
I'm thinking I'll go with the starter battery for the rest of this season and before I winterize it, I'll have the wiring for a second battery done professionally.

Right now the GPS isn't set up (more rocket science)and the VHF, Fishfinder and lights can be turned on only as needed, so I'm sure I'll be able to slip by for a couple more months with the starter battery.


wriling posted 07-29-2004 08:30 PM ET (US)     Profile for wriling  Send Email to wriling     
Hi Dave,

Just read your post after I sent mine up. The deep cycle battery that was in the boat is totally dead. Like a doornail.

The fellow that I bought my boat from had a starter battery from his new boat that he wasn't using so he gave it to me to replace my dead deep cycle. I had that starter battery checked by the mechanic here at work (Chevrolet dealership)and he said it was good, did a load test etc.

When I get home I'll get the specs on this starter battery and see if they match up to your info. I certainly have no reservations about buying a brand new one right off the shelf if that's needed.

Also, my Evinrude 90 didn't come with a manual. Is there a place online that I could get that info?


davej14 posted 07-30-2004 09:32 AM ET (US)     Profile for davej14  Send Email to davej14     

If you have a new battery in good condition I would not rush out to replace it. Enjoy the season, most boaters do not have "AGM" batteries and I personally wouldn't consider changing it out until next season. When you winterize, be sure to remove the battery you have and store it where it will not freeze. Conventional batteries lose their charge while just sitting dormant and once this happens the liquid within them can freeze, cause irreversable damage and possibly crack the case. If you do not replace it, be sure to have the it charged and check the fluid level before reinstalling next year.

If you replace the battery in the Spring, check out the Optima 34M at:

This is the one I went with, and unles your Evenrude has an unusually high CCA requirement it should serve you well. You will not have to remove it in the winter or charge it in the spring and it is totally sealed. Shop around on the web for the best price but watch out for shipping charges, these things are heavy. I bought one locally for $119.00 + tax.


erik selis posted 07-31-2004 04:49 AM ET (US)     Profile for erik selis  Send Email to erik selis     

Here is a link to where you can order a manual on-line. Hope this helps.


jimh posted 07-31-2004 10:32 AM ET (US)     Profile for jimh  Send Email to jimh     
Please append comments to the original thread:

Please do not initiate duplicate discussion in multiple threads.

[Thread closed]

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