Battery for new Mercury efi Elctric Start

[solo]

Hi Folks,


I'll soon take delivery of a new Mercury 15 Hp EFI for a Rigiflex 360. It will have electric start and used for teaching sailing on a small lake. What battery should I fit for the electric start? There will be some start/stop during sessions which will last circa 2 hours. I plan to fix the battery in a box attached to the transom under the engine. As the engine is only 330 cc, I'd think that a small motor cycle battery might be a good choice and to keep weight down, wondering about lithium ... but open to all suggestions.

Thanks all, Brian

[Pikey Dave]

Originally Posted by solo

Hi Folks,


I'll soon take delivery of a new Mercury 15 Hp EFI for a Rigiflex 360. It will have electric start and used for teaching sailing on a small lake. What battery should I fit for the electric start? There will be some start/stop during sessions which will last circa 2 hours. I plan to fix the battery in a box attached to the transom under the engine. As the engine is only 330 cc, I'd think that a small motor cycle battery might be a good choice and to keep weight down, wondering about lithium ... but open to all suggestions.

Thanks all, Brian

The owners manual should specify a battery size.

[chipko]

[solo]

Yes that ties up with the manual I found online. 350 CCA is a lot of cranking current = quite a big lead acid battery that I don'twant to carry around. The engine is just 330 cc so what surprises me is that large motorycle engines seem very happy with much smaller matteries than specified for this engine.
I've started looking at lithium as a more realistic solution for a boat that only weighs 120 Kg.

[Pikey Dave]

Originally Posted by solo

Yes that ties up with the manual I found online. 350 CCA is a lot of cranking current = quite a big lead acid battery that I don'twant to carry around. The engine is just 330 cc so what surprises me is that large motorycle engines seem very happy with much smaller matteries than specified for this engine.
I've started looking at lithium as a more realistic solution for a boat that only weighs 120 Kg.

350CCA is quite small actually. A bog standard car battery will be circa 800cca.
Tbh electric start on an engine that size is a bit of an extravagance unless you have a good reason for needing it.

[solo]

Good points Dave. The good reason is that we are an RYA training centre. We must stop engines when we are alongside people who have capsized and are in the water. Electric start encourages the crew to stop the engine if they know they can restart it easily.

[Peter_C]

I would do Lithium or LiPo, but it MUST be 100% sealed or bad things happen in salt water. You can make one easy enough using cells, but it must fit into a sealed container like a canister for a scuba diving light. Otherwise an AGM is more compact and better sealed than a flooded lead acid battery. Both will take a specific voltage regulator to keep the voltage down.

Buying a Lithium 12 volt jump pack and modifying it might be the easiest and cheapest way to get a battery. It will still require a 100% sealed container.

[beamishken]

An 063 car battery will do everything you need & won't need special boxes or attention, cost about 40 quid & will last a good few years weighs 12kgs ish but not the end of the world in the grand scheme.
Its easy to over think things & before you know it your into an expensive complicated project.
Simple is often best imho

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