What's with the rooster tails?

[chesapeake724]

I've taken two trips so far and the last one was on a really calm day. I looked back and noticed that there seems to be a lot of spray coming up behind the transom. ('87 Step w/ 175 Johnson on a notched transom. Is it because the keel is flatter? Maybe it's because I've had an underpowered boat or the other one had a bracket. Performance doesn't seem to be affected, but on either side of the motor there's pronounced spray shooting up high. Anyone else notice this?