There's another thing to throw into the mix. 3 and 4 blade turn much different. You should try both and see what you boat likes. And your not to deep for 4 blades. They work fine buried

4 blades due work fine buried, especially on twins. However, in my experience singles on hulls that like bow lift typically like a 3 blade over a 4 blade. As stated, try both and see what's best for your needs on your particular hull..