A different prop will defintely help (depending on what you have now)
I have a 19ft Stingray I/O (4.3L EFI)
I first switched to a 4 blade 21 pitch aluminum and had a significant improvement
Next I went to a 5 Blade stainless Steel 21 pitch - Awesome prop!!
The 5 blade stainless is definitely the way to go.
You have to figure out which pitch is right for you, I tried a few out from 19-25.
The 19 pitch perfomed best for holding slow speeds but I lost too much top end.
The 25 pitch surprisingly held speed as well as my 3 blade and could get the boat close to 60mph.
I found the 21 pitch a good balance of holding speed but I can still get the boat close to 50mph
Also a HUGE improvent is slow speed handling such as docking etc...
In my opinion it was worth every penny
It's amazing what the right prop can do for you!