motor slips and grabs

I have an 89 Ranger 393 with 225 excell when i trim it up it will slip for 4 or 5 seconds then bite again . It goes back and forth. The Ranger has two steps underneath and the cavitation plate is about 1 inch higher than the bottom of the transom. Should it be even with the bottom of the boat or the transom?

[boats.net]

You might try to lower motor one hole to see if helps.