Bad Lower Unit, small crack developing at trailing edge

[sschlachta]

1985 Johnson 235 V-6<br /><br />Recently replaced lower unit with a v-8 lower (comercial v-6) but have noticed a fine crack develop at the trailing edge of the LU where the prop meets lower after just 3 hours of use. I am going to return the LU were I purchased it. <br /><br />What can I look for to ensure that a Lower unit is in fact a good one?<br /><br />Is there any value in a v-8 lower in having it fixed? or is there something wrong/ unbalanced with the carier of this lower unit?<br /><br />What is a good prie range for a used Lower unit? New Lower unit?<br /><br />Any advantages to be gained by a newer style Lower Unit?