Outboard propellers as well as the design and development of boats have both been dramatically influenced by Technology.

The three key factors affecting performance have not changed.

Outboard Propellers are very exposed and vulnerable.

Do you enjoy the security of a spare prop on board your boat?

You wouldn't go anywhere without a spare wheel in your car ... would you?

Everything You've Always Wanted To Know About Boat Propellers.

Boat Propellers and finding the "Perfect Prop" for your boat can be confusing so let's have a quick look at the basics.

How Do Boat Propellers Work?

A boat propeller rotates ... the blades of the boat propeller push water in one direction causing boat movement in the opposite direction.

As the boat propeller pushes water back a vacuum is created on the forward side of each propeller blade. This vacuum pulls on the boat propeller blade and helps move the boat forward.

The strength of the vacuum increases as the boat propeller spins faster ... pushing a greater volume of water back ... both effects combining to increase the forward speed of the boat.

How Are Boat Propellers Identified?

Propeller sizes are identified with two numbers ... usually expressed in inches. The first number is the diameter of the boat propeller and the second number is the pitch.

The pitch is the theoretical distance a boat propeller moves forward in one revolution.

So ... if you have a boat propeller with a diameter of 14 inches and a pitch of 18 inches, the propeller configuration would be: "14x18."

Outboard Propellers.

The centre part of an outboard propeller is called the "hub." This is the part which connects the outboard propeller to the propeller shaft.

The image above illustrates a thru hub exhaust outboard propeller in which the engine exhaust flows through the outboard propeller.

This is the style of most of today's outboard propellers including an Evinrude propeller, a Honda propeller, a Johnson propeller, a Mercury propeller, a Mercruiser propeller, a Mariner propeller, a Cobra SX propeller, an O.M.C. Cobra 800 propeller, a Suzuki propeller, a Volvo Penta propeller, a Volvo S.X. propeller, a Yamaha propeller plus a Tohatsu propeller ... in fact just about any brand of modern outboard propeller and most sterndrives.

They are easily identified by the barrel around the hub to which the outboard propeller blades are attached.

Outboard Propeller Facts.

Propeller design has managed to keep pace with technology over recent years while the design of boats has changed significantly and the development of outboard propellers has been dramatic.

In spite of those improvements ... the three key factors affecting the performance of your boat have not changed.

We're talking about weight ... horsepower and the outboard propeller.

Making a boat lighter or buying a more powerful outboard motor just to improve performance or economy are options most people would not consider.

This only leaves the all important outboard propeller so lets look at the basics and discover how to find the perfect outboard propeller for your pleasure boat ... or fishing boat.

The perfect outboard propeller for you is one which will allow your engine to develop wide open throttle (W.O.T) RPM with your normal load aboard while staying within the maximum RPM range recommended by the manufacturer of your outboard motor.

Engine manufacturers state that rev-range as part of the engine specifications.

Damage to your outboard motor is likely to occur if an outboard propeller is fitted which allows the engine to over-rev, or exceed the manufacturers specified R.P.M. at W.O.T.

Serious engine damage is also likely to occur if the installed outboard propeller overloads the engine making it impossible for it to reach the minimum specified R.P.M. at W.O.T.

Top speed and best acceleration is achieved when your RPM at W.O.T. is near the midpoint of the manufacturer's recommended maximum RPM range.

That's a good outboard propeller ... but it may not be the perfect propeller for your application.

Consider the following ...

Most outboard propellers are so exposed it's only a matter of time before they become seriously damaged.

Worse still ... an outboard propeller is so vulnerable it could even become totally destroyed ... and very often is.

It's just as well you carry a spare prop on board your boat ... you do ... don't you?

CRUNCH ... BEND ... BREAK.

There it goes again ... now ... remember where you put that spare outboard propeller ... that's right ... you stowed it where you could find it quickly in an emergency ... didn't you?

Sound Familiar? ... Thought so.