Battery hook up

Hook one battery's positive terminal to the second battery's negative terminal. Now, the first battery's negative terminal is the ground and the second battery's positive terminal goes to the starter.

This is connecting them in series, the voltages add. For the record, I use one 12V battery in my 354.

Roger,

The cold cranking amps you  need will depend on where you're located, temperature-wise.  I'm in the tropics and my 304 Jinma tractor has direct injection so it starts with only a half-second's cranking.  If you're in a place where the temps drop below freezing, then you'll want all the cranking power you can get –  just buy the biggest battery that will physically fit in the battery well and you'll be fine.  If you have really cold temps you may also want to invest in a block heater or other means of warming the oil and battery to get the best starting possible.  Whatever you do, don't try to economize by getting a minimal battery – you'll only kill it off early due to overworking it.  The price difference between a battery with 600 cca and one with 900 cca isn't that great.

I agree with Rich. I am in a cold climate, I always get the biggest battery with the largest CCA I can find, expense is a smaller concern. In my 354, I installed a Group 31 31-XHD 1000 CCA from Interstate, it wasn't cheap, $150 or so, if I recall!!!!!