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Old 08-05-2021, 19:51   #1
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9.9 yamaha 12 volt battery size

Anyone know what is consided to be the correct size 12 volt battery should be for a 9.9 yamaha 4 stroke electric start outboard.

I currently have a 120 AH and need to change and I think 120 AH is too big, the only use for this battery is starting as it is not connected to anything else.

Thanks
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Old 08-05-2021, 19:56   #2
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Re: 9.9 yamaha 12 volt battery size

A motorcycle battery will start one easy.
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Old 08-05-2021, 20:45   #3
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Re: 9.9 yamaha 12 volt battery size

Thanks, any specs you can share?
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A motorcycle battery will start one easy.
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Old 08-05-2021, 20:59   #4
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Re: 9.9 yamaha 12 volt battery size

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Thanks, any specs you can share?


Hereís a quick list of suitable batteries.

https://shop.advanceautoparts.com/c3...E&gclsrc=aw.ds

You could use just about anything small.
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Old 08-05-2021, 23:25   #5
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Re: 9.9 yamaha 12 volt battery size

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Thanks, any specs you can share?
I think the mc equivalent engine size at a rough guess is about a 250cc. I used (iirc) an 18ah jet ski battery (pretty much the same as a mc battery) on my Yamaha 9.9 many years ago. Never had a drama with it and it's only charge source was the motor's alternator.
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Old 08-05-2021, 23:32   #6
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Re: 9.9 yamaha 12 volt battery size

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Originally Posted by geoffq1 View Post
Anyone know what is consided to be the correct size 12 volt battery should be for a 9.9 yamaha 4 stroke electric start outboard.

I currently have a 120 AH and need to change and I think 120 AH is too big, the only use for this battery is starting as it is not connected to anything else.

Thanks


120Ah or 120CCA? FWIW my 900 Yamaha bike has a 16Ah, which would be something like 120CCA. A 9.9hp should be able to start with 10Ah ie approx 70CCA.
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Old 08-05-2021, 23:35   #7
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Re: 9.9 yamaha 12 volt battery size

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120Ah or 120CCA? FWIW my 900 Yamaha bike has a 16Ah, which would be something like 120CCA. A 9.9hp should be able to start with 10Ah ie approx 70CCA.
120 AH, I have not been able to confirm the CCA yet.
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Old 08-05-2021, 23:43   #8
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Re: 9.9 yamaha 12 volt battery size

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Originally Posted by geoffq1 View Post
Anyone know what is consided to be the correct size 12 volt battery should be for a 9.9 yamaha 4 stroke electric start outboard.

I currently have a 120 AH and need to change and I think 120 AH is too big, the only use for this battery is starting as it is not connected to anything else.

Thanks
Specs for 10/20 hp honda (electric start) is 35 amp/hr 270 cca
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Old 09-05-2021, 04:17   #9
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Re: 9.9 yamaha 12 volt battery size

Our Suzuki DF-15A electric start outboard battery spec: 450 MCA or 330 CCA, 70 minutes RC. The 9.9-hp version they eventually introduced was on the same basis platform, so battery specs probably would have been the same.

I used a Deka Outdoorsman 11U1L flooded battery at first, but we didn't run our dinghy often enough to keep that FLA battery well-charged. I eventually changed to a Deka Intimidator ETX-30L AGM battery to deal with that self-discharge issue.

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Old 09-05-2021, 08:52   #10
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Re: 9.9 yamaha 12 volt battery size

My aux is a 9.9 Chrysler. I have been using a $20 golf cart battery for many years. Has never failed me.
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Old 09-05-2021, 12:13   #11
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Re: 9.9 yamaha 12 volt battery size

Don't over think the battery size. Just get the smallest 12V golf cart / riding
lawn mower battery your supply source has and you'll be fine. JMHO
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Old 09-05-2021, 23:50   #12
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Re: 9.9 yamaha 12 volt battery size

I had a 6 lb lithium battery for my 200 hp/ 1340 cc Hayabusa. It never had a problem starting the beast. Forget lead or agm. Go lithium.
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Old 10-05-2021, 00:26   #13
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Re: 9.9 yamaha 12 volt battery size

I am a big fan of lithium but for a starter battery I think it's just overkill. As others have mentioned, a simple motorbike starter battery will do, my 1200cc bike starts with a battery that cost me 30 usd.
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Old 10-05-2021, 02:04   #14
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Re: 9.9 yamaha 12 volt battery size

Hi Geoff,
I have attached the link to a battery company and their application guide.
For Yamaha (if it was me, I would be asking Yamaha) they quote all engines below 25hp they quote 40ah @20ah rate.
For a Honda of a similar size on the same site they quote 35ah @ 20ah rate.
I believe its a mistake to think bigger is better because, If the only source of charging this battery is the engines alternator then if the batter is too big, it will potentially never get fully charged.
To put things in perspective, My Yanmar 3 cylinder 30hp diesel inboard only needs a 70amp/hr so your 120 amp/hr is grossly oversized unless you can recharge it from another source!

http://www.dekabatteries.com/assets/...ionslayout.pdf

All the best
Colin
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Old 11-05-2021, 07:42   #15
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Re: 9.9 yamaha 12 volt battery size

A lawn tractor battery would work. I have used them on my full-sized tractor for years with 40 horsepower gas engine.
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