[400A]

I agree 100% with Marshall, but in the "for what it's worth" column I had the same issue a few years back. I cleaned all connections twice and made sure the ground was super clean. Changed the battery and starter. Same issue. In frustration and as a last resort I changed the battery cables. That solved the problem! Afterwards I slit the insulation off the negative cable and even though it looked fine on the outside, the copper was badly corroded under the insulation. You just never know ......