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唔知點好1?

Outboard車葉要點簡?
1. 車葉尺寸的大小
2. pitch 大(16)小(12)
3. 車葉的物料. 不锈鋼, 鋁合金, 銻..
以上3樣o野對engine, 行船(example, 起步)有咩影響? 不同車葉物料又有咩特點?

Re: 唔知點好1?

How To Choose A Propeller

Selecting the right propeller is an important factor in maximizing your boat's performance, while allowing it to operate in the recommended rpm range. Determining the correct size and style of prop will keep the engine from over-revving, while allowing it to achieve the maximum horsepower at the lowest rpm's.


General Rules to Follow:

A 1 inch reduction in propeller pitch will result an an increase of 150 to 200 RPM at full throttle.

If at full throttle, the engine RPM is too high, you will need to try a propeller with either a higher pitch or larger diameter. Conversely, if the engine RPM is too low at full throttle, try a propeller with a lower pitch or smaller diameter.

Due to the differences in hull designs, engines, and weight (and weight distribution) from one boat to another, finding the correct propeller for each boat will vary.

Finding the best propeller can only be accomplished by trial and error after determining what is most important to you (speed, handling, etc.) under specific water conditions (lake, ocean, rough seas, etc.)



What is your engine's recommended propeller diameter and pitch ?

- Props are described by referring to diameter and pitch. Diameter is twice the distance from the center of the hub to the tip of any blade. Generally smaller diameter props correspond with smaller engines and boats or higher speeds. Larger diameter props correspond with larger engines and boats or slower speeds. Pitch is the forward movement of a propeller through one complete revolution. Pitch can be thought of as speed. The higher pitch prop the engine can turn, the faster the boat will usually go.


3-blade or 4-blade Propeller?

- Sufficient blade area is needed to properly distribute engine power across blade surface. Too little blade area causes high "blade loading", which means the prop can't absorb all the power transferred by the engine. With increased blade are you can decrease the blade diameter, but often with less efficiency at higher speeds. A 3-blade prop is considered the best combination of blade area and low blade loading. When the number of blades is changed, diameter and pitch may require a minimal adjustment to remain in the safe blade loading range. For most purposes 3 and 4-blade props can be used interchangeably on outboards and sterndrives (I/O) without much of a change in performance.

Basically the difference between using a 3 blade or 4 blade propeller can be seen in the boat's handling and performance. Three-blade propellers are the most popular and are good for general, all-purpose use. They provide good acceleration and control, and excellent top speed performance. Please note: Aluminum propellers are ONLY available in a 3 blade design.

The 4 blade design (stainless steel)is popular with boaters who are looking for a good hole shot, better acceleration, and better bow lift (higher trim angle) to reduce boat drag (too much of boat in water- reducing top end speed).
Important: 4 blade designs allow your boat to stay on plane at a lower rpm - Producing a slower cruising speed without loss of plane of the boat in rough seas and conditions.
Renegade props (4 blade) are of an excellent design -allowing better top end, speed, with minimal drag.


Material: Aluminum or Stainless Steel ?

- Propellers are made of either composite, aluminum, or stainless steel. Composite props are good, durable, and inexpensive. Aluminum props are the most common. They are suitable for the widest range of applications. Stainless steel props offer higher performance and better durability.

Cupped Propellers - Special curved trailing edges enable the prop to cut through the water better. Cupped props allow most boats to achieve a higher top-end speed or at least the same speed at a lower engine rpm. They also promote more efficient fuel consumption.


Wide Open Throttle (WOT) rpm Range

- When selecting a prop, the goal is to choose one that allows the engine to reach its optimal WOT. This is generally between 5000 and 5500 rpm, depending on engine type. This information is usually included in the owner's manual of a new boat or engine.

If your current prop's performance is within manufacturer's WOT guidelines, choose a replacement prop which duplicates the diameter and pitch of your current prop. You might consider upgrading to a different material such as stainless steel.


If your current prop is unsatisfactory?

- What if your engine operates at the wrong rpm at WOT? Pitch and rpm have an inverse relationship. Increasing pitch reduces rpm and reducing pitch increases rpm. A 1" change in pitch will result in a 200 rpm change in engine speed. Therefore, if your engine operates below the proper rpm, consider a propeller with less pitch. If your engine over-revs, consider increasing the pitch.
You might also consider changing the propeller size to affect a specific performance attribute. A lower-pitch power prop makes it easier to pop skiers out of the water. Tournament bass boats may need more top end speed and should use a prop with a higher pitch. Houseboats and cruisers care more about efficiency at displacement speeds, therefore they require a lower pitch to achieve low-end power and the largest diameter their lower unit can handle.


Boating Activity (Cruising, Fishing, Racing, Skiing...)

- The type of activities you do with your boat are important in determining what type of propeller you will need.
You may need to have more than one propeller if you use your boat for different types of activities.

The Truth: No single propeller will be able to give you top speed and handling under all conditions.
The propeller that provides the best hole shot will probably not provide the best top speed for your boat. A propeller that will give you absolute top speed, will probably provide uncomfortable midrange handling or ride.

If you use your boat often under a variety of conditions, you will probably decide that you need more than one propeller. Eg. one for cruising, one for speed and one for pulling skiers... of course, if your budget only allows one good quality propeller, you will need to select the propeller that provides the best compromise between the characteristics you are looking for.

Re: 唔知點好1?

are different brands of propellers (if they are of the same size and pitch) interchangeable? would there be any risks and disadvantage in using prop other than the same brand as the OB itself. Most of the original props are quite expansive. Has anyone tried overseas brands thro the net?