I have a group 27 marine battery from Costco. If I was to do it again I'd get am optima because it is in a smaller package. I have a yanmar 3gm30. Sent from my iPhone > On Jul 24, 2017, at 3:16 PM, Dan <danb70341 at gmail.com> wrote: > > What cracking power is needed for a starting battery to start a 30 hp westerbeke? > Thanks > > Sent from my iPhone