Correct size 12 volt battery for a 9.9 Yamaha 4 - stroke electric start outboard.

[Rum_Pirate]

What is considered to be the correct size 12 volt battery should be for a 9.9 Yamaha 4 - stroke electric start outboard.

Having difficulty getting info googling.

Can get AGM type here (in this far flung corner of the globe) . . . but made in Korea.

The only other draw on the battery would be mast head navigation lights (very little if any night sailing planed but would be good to be prepared) and a vhf radio.

 

[rgh27]

I've installed the following on my boat for my 9.9HP 4-stroke Yamaha electric start outboard - Numax MV22MF Marine Battery 75Ah. Numax MV22MF Marine Battery 75Ah

I've installed a 30W solar panel to keep the batteries topped up.

 

[ylop]

I've used the smallest car battery I could buy in halfords for a rib with bigger engine than that in the past. I've also known car jump start batteries do a decent job on small boats. Basically if its 12V and starts a car or motorbike you'll be fine.

 

[VicS]

I've used the smallest car battery I could buy in halfords for a rib with bigger engine than that in the past. I've also known car jump start batteries do a decent job on small boats. Basically if its 12V and starts a car or motorbike you'll be fine.

+1 for a small car battery.
Halfords if you must, but I'd avoid their cheapest, otherwise from Tayna or Battery Megastore.
But make an estimate of total other loads which will be dependent on the battery eg nav light(s) while sailing or interior lights while moored or anchored and increase the size of battery if necessary to avoid more than 50% depth of discharge, also consider the merits of a 'leisure battery' which should be better at supplying a small current continuously for several hours than an engine start battery.

Also look at using a small ( upto say 10 watts) solar panel to keep the battery well charged.

FWIW, I have a 60 Ah leisure battery and a 5 watt solar panel (permanently mounted) but a rope start outboard with minimal battery charging capability. It's just enough for weekend sailing . They are the largest battery and solar panel which will fit the allocated spaces

 

[Boathook]

What is considered to be the correct size 12 volt battery should be for a 9.9 Yamaha 4 - stroke electric start outboard.

Having difficulty getting info googling.

Can get AGM type here (in this far flung corner of the globe) . . . but made in Korea.

The only other draw on the battery would be mast head navigation lights (very little if any night sailing planed but would be good to be prepared) and a vhf radio.

Nearly any motorbike battery will do but you do need extra for the nav lights and vhf plus possibly instruments and interior lights. Make sure that all the lights are led and use the battery out of your moke ....
If you do buy a battery purely for the boat fit a small solar panel and a simple regulator.

 

[Hot Property]

I use something similar to this

Halfords HB063 Lead Acid 12V Car Battery 3 Year Guarantee | Halfords UK

For my 100 hp Honda outboard. Plenty of power for lights, VHF etc. If you have electric start you also have an alternator to charge the battery so no problems there.

A 75 amp battery is just overkill, unless you have high loads when engine not running.

 

[Steve65]

Any 12v car battery is fine

 

[Chiara’s slave]

I assume this is for the Farrier? We had a 75AH leisure battery. Cranking a 9.9 is well within their capability.

 

[Cariadco]

Does the 9.9 have an Alternator?

 

[Chiara’s slave]

Does the 9.9 have an Alternator?

Anything with electric start is going to have one. It won’t have a massive output, the charge current isn’t an issue for any battery that will crank the motor.

 

[Cariadco]

Anything with electric start is going to have one. It won’t have a massive output, the charge current isn’t an issue for any battery that will crank the motor.

I asked, cos my old Mercury 80HP, had eleci Start but No Alternator!!

 

[VicS]

The battery requirements are detailed in the owners manual

 

[Chiara’s slave]

I asked, cos my old Mercury 80HP, had eleci Start but No Alternator!!

That must be pretty ancient, I’ve owned Mercury outboards on acRIB from the early 80s, they had alternators. How on earth does it work without? Had a previous owner just removed it?

 

[andsarkit]

The battery requirements are detailed in the owners manual

What would happen if you exceeded the CCA rating? I can't imagine why it would be a problem.

 

[VicS]

What would happen if you exceeded the CCA rating? I can't imagine why it would be a problem.

Dont know.
Some of the older VP engine manuals specified a maximum battery size'

Pure guess ........ A excessively large battery might deliver a high enough current to a stalled starter motor to do damage (burnt out windings)

 

[Rum_Pirate]

What would happen if you exceeded the CCA rating? I can't imagine why it would be a problem.

I would like to know that as well. Will start separate thread for more participants.

 

[fredrussell]

That must be pretty ancient, I’ve owned Mercury outboards on acRIB from the early 80s, they had alternators. How on earth does it work without? Had a previous owner just removed it?

Smaller outboards don’t have alternators - they have a charging circuit based around a fairly simple coil setup on the stator plate.

 

[Refueler]

Personally I like to go for largest capacity ... and good CCA rate as I can afford / fit in the space ..... why skimp on it ??

If I have to lift out and carry home for charging ... then maybe two small identical batterys to make up a large capacity ... but then easier to carry each one. Only thing with smaller batterys then is often their CCA is lower.

9.9hp ......

My Lawn Tractors .. one is 13.5hp ... other is 18.5hp .... both 4str ... each one has a small about 30A/hr Lead Acid .... no problem starting those .... no idea what CCA they are ...

 

[AngusMcDoon]

Smaller outboards don’t have alternators - they have a charging circuit based around a fairly simple coil setup on the stator plate.

Technically, and pedantically, they are still alternators. Magnetos are a sub-set of alternators having permanent magnets. I accept that the common use of 'alternator' doesn't apply to charging coils found on small outboards.

 

[VicS]

Smaller outboards don’t have alternators - they have a charging circuit based around a fairly simple coil setup on the stator plate.

According to Yamaha their 9.9 has an alternator