Bravo 3 vs Bravo 1

[Geewest]

In the "50mph Bennington" thread the subject about twin prop Vs single prop came to mind. I would like to hear from owners about the pros and cons of bravo 3 ( twin prop) Vs single prop. We currently have a single prop bravo 1 I/O

Dealer says pros of Twin prop are

1. Backs up straight ( I have not had a problem with the boat backing up better to one side Vs the other) boat seems to back up even

2. Less cavitation in hard turns ( our 2575 RLI/O does cavatate in hard turns) our boat has lifting strakes on insides and out sides of all 3 toons

3. Tracks straighter ( I have never noticed a problem with our boat not tracking straight)

Cons

1. Less top speed 2-3 Mph

2. I can't help but THINK that the twin prop could be more maint ect. Not sure but just thinking. If you strike a prop Now you have 2 bent props instead of just one.

3. Replacement props not as common and more expensive.

Your thoughts

 

[Butchkid]

I am about as far from an expert as you can get on this. In fact, I would qualify as completely clueless if your post wouldn't have motivated me to go online and look. Now I know more than I did before, but I also don't believe everything I read. This is what I found as to why Duoprops were created. It is interesting that they believe something different than your dealer believes.

Duoprops are just what their name would suggest--counter-rotating twin-propellers used in place of single-screw installations. Studies by Volvo Penta and others have indicated that two propellers are indeed better than one. Why, however, is this the case? Many of the major advantages of dual-propeller systems come from 1) a reduction in "propeller slip," and 2) the reduction in cavitation-related inefficiencies.Propeller slipping occurs when a single propeller churns the water. A propellor moves in much the same way a screw does. However, while a screw has a solid environment (such as wood) in which to work, a propellor must deal with a less-resistant world of water and, sometimes, air. The inefficiency created by non-uniform resistance to each propeller turn decreases both fuel efficiency and speed. The degree of propeller slipping is directly proportional to the pitch of the propeller.When a propeller moves through the water, the pressure on the reverse side of each blade becomes less. At some point, the pressure becomes so low that the water begins to "boil" and bubbles of steam are formed. This cavitation, and the air and bubbles from it, makes the blades of the propeller act as if they are thicker and increases the resistance of the water to the propeller blades. This not only decreases efficiency, but over time can cause damage to the actual blades as the bubbles travel to where the pressure is higher and implode.

Duoprops solve the problems of propeller slipping and cavitation through the presence of a second counter-rotating propeller that allows for decreased pitch in each of the two propellers and helps to break up the formation of the air and steam bubbles. Two propellers working in tandem are able to deliver better fuel efficiency (by 15 percent) and increased accuracy when moving in reverse. Thrust and acceleration will increase at slower speeds (by 15 and 20 percent, respectively), and top speeds will also increase thanks to reduced propeller slipping. Duoprops also suffer less cavitation-related damage.

 

[Earnit]

I own a 2008 2575RCW ESP package with a Volvo 5.0 FI with Dual Prop. I have hit 50MPH with the Bimini still on the boat with the gates open. The dual prop is great for out of the hole I can yank a 300# guy out of the water on a wake board, the turning radius is also better with it, tracks and it steers better at slow RPM at the dock.