Transom height question

[linesider36]

I will be hauling my '79 24' CC on Monday to rebuild the transom.On other threads I've been following the consensus seems to be raise it to 30". So the question is will a 25" '98 Johnson 225 work on a 30" transom both efficiently and safely. Will cavitation be a problem when you need the power the most ie. inlets, following seas, etc. Re powering isn't in the cards right now but I don't want to do this repair again to raise it. Thanks guys, Classic SeaCraft Rocks!