Outboard Engine Starter Cranking Currents?

[C08]

Any ideas what the cranking current would be for a 20hp outboard. I currently have 5 x110AH batteries configured as a 3 and 2. They are all leisure batteries which at times do get over -discharged even so they have all done 5 years of use & abuse. I have a wind generator and 2x80w solar which keeps the batteries well up and balances fridge tv etc very well except for several days at a wet and dull anchorage. I am going to start to replace batteries and I am wondering about re-configuring the banks. I could have a bank of 4x110v leisure and 1x starter battery as I will have a 30hp outboard that will hand start if necessary in emergency. Is a 4xleisure and ixstarter battery my best option or are there other better combinations?

 

[sailorman]

Any ideas what the cranking current would be for a 20hp outboard. I currently have 5 x110AH batteries configured as a 3 and 2. They are all leisure batteries which at times do get over -discharged even so they have all done 5 years of use & abuse. I have a wind generator and 2x80w solar which keeps the batteries well up and balances fridge tv etc very well except for several days at a wet and dull anchorage. I am going to start to replace batteries and I am wondering about re-configuring the banks. I could have a bank of 4x110v leisure and 1x starter battery as I will have a 30hp outboard that will hand start if necessary in emergency. Is a 4xleisure and ixstarter battery my best option or are there other better combinations?

I have a 500cc single cylinder Lawnmower it has a dinky AGM to start it.
how will you charge those 3 x 110Ah batteries ( Note to VicS see spellin )

 

[duncan99210]

I’ve got five batteries in the domestic bank and a single battery for engine starting purposes. They can be linked if required but never needed to do so. For what it’s worth, I’d always have a single engine battery and a separate domestic bank. As for power requirements, I used to have a motorboat with a 75 hp outboard and used a 70 amp hour battery for starting it: more than adequate as I suspect it would have happily started off a motorbike battery.

 

[C08]

Interesting what size is the small AGM battery for your lawnmower? My 3.5hp Bowthruster has a 300A fuse, which make me wonder how much less than the typical cranking current of 6-700CCa for a car or normal boat engine is a moderate sized outboard?

 

[macd]

My 3.5hp Bowthruster has a 300A fuse, which make me wonder how much less than the typical cranking current of 6-700CCa for a car or normal boat engine is a moderate sized outboard?

The starter motor will draw quite a lot less. A comparison of the rating of the bow thruster motor with the outboard stater motor should give a useful guide. Thruster is probably in the region of 3kW, starter less than 1kW; you should have the figures in your handbooks.

 

[VicS]

Any ideas what the cranking current would be for a 20hp outboard. I currently have 5 x110AH batteries configured as a 3 and 2. They are all leisure batteries which at times do get over -discharged even so they have all done 5 years of use & abuse. I have a wind generator and 2x80w solar which keeps the batteries well up and balances fridge tv etc very well except for several days at a wet and dull anchorage. I am going to start to replace batteries and I am wondering about re-configuring the banks. I could have a bank of 4x110v leisure and 1x starter battery as I will have a 30hp outboard that will hand start if necessary in emergency. Is a 4xleisure and ixstarter battery my best option or are there other better combinations?

4 x 110 Ah domestic bank + 1 starter battery will be your best bet


The service manual for 25hp and 30 hp Tohatsus says:

Installation of Battery

When using battery, select the one with capacity ranging from12V 70AH (350CCA or 465MCA) to 12V 100AH(775CCA or1000MCA at below freezing temperature).

1 Battery should be stored in battery storage box andsecured to hull to prevent it from falling due to rolling orpitching or any shock in the place where it is protectedfrom water spray.
2 When connecting battery cables, connect positive cable(red) and then negative cable (black). (Reverse the orderwhen disconnecting.)Positive cable is the one with red tube on the terminal end.​

I'd regard a 70 Ah /350 CCA battery as being generously sized to start a 30 Hp outboard