Starter battery size CCA

I'm looking to install a separate start battery for my swanson It currently has just one battery bank .
the engine Is a Lister stw3m 30hp with a 3.2kw starter motor max current draw of 280amps on the clamp meter.
many CCA do think Ill need?

If your sticking to one battery then I would suggest the largest deep cycle battery that fits in your battery box.

I replaced my old starter batt. with an SSB 105ah AGM from Batteryworld last year thinking of my home batt bank (2x105's) carking, I would still have something to fall back on to run nav.equipment, lights etc. for safety's sake. Not a place saving few quids. Methinks.

Hi thanks for every ones input freeradical that battery table is excellent cheers
I think ill go for a 500-650cca Its tight on space and I was worried it might be to small but seems more than enough
I was thinking one with caps to top up water but a agm battery does look like a good option it will be trickle charged by a 20w panel/reg
I've just installed a combination battery switch a make before brake type to split charging from the 75amp alternator with soon to be install sterling alternator regulator.
I'm looking at 2x 335ah 6v fullriver agms for house as the will fit where the old battery's are again concerned it might be a little small for cruising and around 400w of solar for charging once installed

The size of your house battery and its charge system is directly related to how much power you use ie, I have a 130 ah battery and 300w panels and don't require extra input, that being said I've lived of the grid most of my life so I guess I've been trained to tread lightly, LED lights and a fridge with a danfoss compressor a small inverter for charging battery tools a car stereo and Internet via iPad (12v charge ). If you want to run a TV, air conditioner, ice cream maker etc you are gunna need moor input and storage, every situation is a bit different so you tailor make it, I looks to me tho you've got a fine and dandy system in mind

I am not sure where you are in Sydney. I am on the boat so don't have the details but I purchased a 135ah AGM dual use battery so it is deep cycle as well as high cranking. From memory it was about $250.
They are in Peakhurst.

I'm thinking this one for the start battery www.centurybatteries.com.au/resources/battery-finder/product/ns70m
620cca should be plenty its the biggest start battery I can fit if install full river agm house battery's

That battery will start an 8 litre Gardner diesel very easily. Your engine alternator would then have that battery recharged in a few minutes. If your only going to have one battery on this yacht with solar panels, victron charger, fridge, radar and autopilot etc and not going to motor sail everywhere then you should be thinking deep cycle battery. Deep cycle batteries will start small diesels like yours easily.
The ideal set up would be a deep cycle battery as the ships battery and a separate small starter battery for the main engine. The starter battery doing nothing but starting the engine and the alternator recharging that battery. Use a rotary switch to jump start if ever needed or jumper leads or even a charge pack.

wish my swanson had a gardner 6lx maybe a bit heavy
The plans is to have 2 separate battery's one for start and a house bank 20w of solar for the start and 400w for the house bank hopefully sorted out by spring I've got most of the wiring done just need the battery's and solar panels

j bear how big is your house battery bank and where is it located? , mine is under the aft berth in front of the steering quadrant

cheers jbear ill get some pics up when I'm done to
yeah the lister is a heavy lump around 330kg wish mine was freshwater cooled