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Author Topic:   Starting Battery: 90-HP Two-Stroke
Troutman767 posted 12-02-2005 04:51 PM ET (US)   Profile for Troutman767   Send Email to Troutman767  
I need to replace the battery for my 1987 Mercury 90-HP two-stroke in my Super Sport. Currently it has a 400-CCA, 500-MCA rated Marine battery. Should I opt for a battery with larger current capability? Is there a limit the starter can handle? I was thinking of a 600-CCA, 725-MCA battery. I really do not need the battery for anything other than starting.

What is the recommended battery for this Outboard?



Teak Oil posted 12-02-2005 06:28 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
I would get the bigger battery, at least 600 CCA. My boat had an 800 CCA battery in it when I bought it and there are no problems with it
sosmerc posted 12-02-2005 08:07 PM ET (US)     Profile for sosmerc  Send Email to sosmerc     
I have had very good luck with the 800 MCA SeaVolt starting batteries from West Marine. Be sure to store the battery on a "maintainer" during the off season.
jimh posted 12-02-2005 08:28 PM ET (US)     Profile for jimh  Send Email to jimh     
The harm in getting a battery that is capable of delivering more current than the load demands is just that:

--it costs more;
--it weighs more;
--it is probably physically bigger.

I don't see any electrical reason why a larger capacity battery would not be better.

fourdfish posted 12-02-2005 09:39 PM ET (US)     Profile for fourdfish  Send Email to fourdfish     
The newer AGM batterys are a very good fit for boats, two types out there! The Cabela's flat plate and the Optima spiral. They stand up better to the constant pounding of a boat, can be installed in more different ways, and they are more dependable. I have two, and my son has them in his cars. We like the Optima because they weigh less, take up less room, and are spiral. A lot of boaters swear by them. Look for more info on the internet. However, that being said! these batterys cost two and a half times as much as regular batteries. Sam's Club has the best price if they have them! I paid $140! Some feel they are not worth it.
rtk posted 12-02-2005 09:45 PM ET (US)     Profile for rtk  Send Email to rtk     
Electrical components draw current. The battery does not supply, or input current.

A battery that has amperage specifications that exceed your electrical systems demand will not damage the electrical component. If an electrical component has an amperage draw that exceeds the battery capacity the electrical component or wiring can be damaged.

Some motors do require a certain battery specification to run well. Most of those motors are current technology fuel injected motors.

A Mercury dealer, technician or possibly a service manual can tell you if there is a unique battery requirement for your motor. My Mercury owners manual on my 2003 motor lists the battery requirement.


Chuck Tribolet posted 12-02-2005 10:24 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
An electical component that has requires more current than
the battery can supply will not damage the wiring. What
will happen is that the voltage will go low. And the only
component on a boat that will draw anywhere near enough
current to do that is the starter, and even that is doubtful.
How many CCA is required to turn over a 427 Chevy compared
to your little (relatively speaking) 90 HP Merc.

Mmm, or maybe the anchor windless.

What damages wiring is too much current, and if the battery
can't supply enough, it sure isn't going to damage the
wiring, assuming the wiring was sized to what the electrical
component requires.

A high CCA battery might actually weight LESS by having more
but thinner plates.


Teak Oil posted 12-03-2005 08:28 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
I dont know about you Jim, but if I am going offshore and have engine troubles, I want as many amps as I can get to try to get that motor started, keep the lights going, run the VHF, etc.

If it weighs five pounds more and is an inch longer, well I guess I will have to live with it

jimh posted 12-04-2005 02:04 PM ET (US)     Profile for jimh  Send Email to jimh     
TeakOil--Exactly. There is not much harm at all in having a bigger battery. You allude to the benefits of a bigger battery. I think we both see it the same way. The original question was framed to inquire about the possible harm to the starter motor which might occur from using a bigger battery. As I said above, I cannot see any electrical harm that could occur. The only harm is to your checkbook and the boat weight and room.

The benefits of a bigger battery:

--more stored energy thus longer service before re-charging
--better voltage regulation, particularly during starting.

Bulldog posted 12-04-2005 05:08 PM ET (US)     Profile for Bulldog  Send Email to Bulldog     
I recently installed two 1000cca batteries I purchased at Cabela's (had enough Cabela dollars they were free!)I had looked at the AGM batteries, but noticed a sticker on them saying that the warrenty would be voided if you exceded a certain voltage, I think it was 14 volts. My old Yamahas run in the 15 volt range due to their simple voltage regulators! My batteries are group 24M same size as your smaller battery, get the biggest you can! I think if I ever run out of gas those batteries could get me home by spinning the starters!....Jack

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