[Chris Burkard]

Here is my $.02 worth: (these comments are only valid for a Tiara 3500 Open, as vessels get heavier, longer, wider and higher, it is common to see 4, 5, 6 and even 7 bladed props)

4-Bladed props if done correctly (proper pitch, diameter, blade design and blade cup) will reduce time to plane the vessel, will reduce vibration and may or may not be more efficient at cruising speed, but most certainly you will lose some top end speed.

As mentioned above, you are adding surface area to the propeller by adding another blade, which adds more friction. In order to overcome the increased friction, the pitch of the prop must be reduced in order to maintain the engines proper RPM range. The extra surface area does reduce slippage (slippage is the difference between the theoretical distance traveled forward per rotation of the propeller and the actual distance traveled forward per revolution), but depending on the engine, size, windage (wind resistance created by fishing towers), beam of the vessel and most importantly the weight of the vessel it may or may not increase efficiency.

To make a long explanation as short as possible, if you normally operate your vessel at a medium load (full fuel, 4 passengers and about 500 lbs. of gear, I would stick with the factory 3-bladed props. If you have a Tuna or Marlin Tower and/or you tow a tender and/or you operate normally with 10 of your friends on board, a set of 4-bladed props may offer you some increased efficiency.

Does that make sense?