For most boaters performance/reliability are going to be the most important aspects of a good boat. MC and Indmar have worked together to produce a power package that will deliver just that. Once you start modifying the power package without proper testing and equipment to monitor the effects of the modifications all bets are off. Speed shops are able to offer quality tunes for mustangs, Camaros and such because they can get test vehicles to test with. I seriously doubt many tuners will be able to say that about the engine/boat combination you have. Most likely any engine change you make will result in mixed results with any gains on one end being given up on the other.
If it were me I'd be calling Eric at OJ and getting a recommendation on a new prop. Based on the age of your boat you're probably running older technology and chances are it's not in like new condition either. This would be the safe bet, will cost you far less in the long run and will get you the best bang for you buck. Besides the worst you'll do going this direction will be to end up with a spare prop.