How does the boat run with the 3 blade? Generally, the 4 blade will run a little slower top-end but pull a better hole-shot. The 4-blade will create more stearn lift which should help you plane at a slower speed. You have to look at what you do and don't like about your current set up to see if you should change pitch or blade count. I would try to borrow one before you buy. E-bay also has some great prop deals if you are sure to check the seller's feedback and find a new or slightly used prop.