Brad Wilcox has a report in the Institute for American Values series on black families, about the effect of religion on urban families. Churches are the main institutional anchors of the code of decency in the city, he conclude, and thus are vital to promoting marriage. All families are more likely to marry if they are religious. This is especially notable for black families.
Among parents in all ethnic groups (black, Latino, white), the married are much more likely to be regular church-goers, typically by 20 percentage points. For example, among black mothers, 63% of the married women are regular church goers, vs. 40% among the single mothers. The comparable numbers for Latina mothers are 50 and 33; for white mothers, 42 and 21. Men show similar gaps, though with lower rates of church going than women.
African Americans are the most religious large ethnic group in America. They are also the least married.
Church can't entirely close the ethnic marriage gap. Even religious African Americans with kids are still less likely to marry than comparable people in other ethnic groups. But religious institutions do help close the gap.