What do the numbers mean on a prop?

Propeller Nomenclature—”Prop Talk”

Propeller size is expressed with two numbers, diameter and pitch, with diameter always stated first. Diameter is two times the distance from the center of the hub to the tip of any blade. Smaller prop diameters generally go with smaller engines, or with fast high performing boats.

What do numbers mean Mercury propeller?

The first number indicates the overall diameter of the propeller in inches or millimeters. The second number indicates the pitch in inches or millimeters. They can be separated by an “X” or letters indicating the rotation like RH or LH. Rotation.

How do you read a propeller model number?

McCauley Aircraft Propeller Model Designations

A numerical value at the beginning of the model number in either the first or second position (i.e. B2 or 2A) indicates the number of blades. (This first constant will be followed by a two digit number value between 31 and 37 which reflects a particular McCauley design.)

Where is the part number on mercury prop?

How do I know what size prop is on my boat?

The diameter of the propeller is the circle which the tip of a single blade describes in a complete rotation. It is found by measuring from the centre of the propeller boss to the tip of one blade and then doubling the result.

How do I know what prop fits my boat?

The proper propeller size for your boat and engine combination is based in part on the wide open throttle (WOT) operating range for your particular engine. You can find this in your operator’s manual, expressed in terms of a certain horsepower at a certain r.p.m.

How can I tell what pitch my prop is?

What’s the difference between a 19 21 pitch prop?

Kind of like the distance a screw would move through wood in one rotation. So, in this case, a “21 pitch prop” would move 21 inches forward in one revolution, and a “19 pitch prop” would move 19 inches forward in one revolution.

How do you measure an outboard prop pitch?

What does a 21 pitch prop do?

The Mercury manual defines pitch as “the distance a propeller would move in one revolution if it were moving through a soft solid, like a screw through wood.” For example, a 21-pitch prop would move forward 21″ in one revolution. The lower the pitch, the better the holeshot.

Is a 19 pitch prop faster?

The 19″ prop will give you less of a hole shot but a higher top speed if the motor is strong enough to turn it in the recomended top RPM range.

Where can I find prop size and pitch?

Propeller Sizes are given in a set of numbers, e.g. 13×17 or 19×23 usually labeled on the propeller. The first number is the Diameter (width of the circle of the blades) and the second is the Pitch (theoretical travel distance of the angled blades in one revolution). Two other design features include Rake and Cup.

What does Overpropped mean?

Over propped means the engine cannot achieve its max rated RPM. Under propped means the engine reaches max RPM too easily ie: the boat doesn’t go as fast as one would expect. Both effects are caused by a combination of pitch and prop size.

What is aircraft propeller pitch?

The pitch is effectively a measure of how far the propeller would move forwards in one revolution. The pitch is used to control the speed of the air leaving the back of the propeller. The pitch of a propeller blade changes as you move along its surface from one end to the other.

Is a 3 blade or 4 blade prop better?

The most asked question at the boat shows is almost always “what is the difference between a 3-blade and a 4-blade boat propeller?” The difference between a 3-blade prop vs a 4-blade prop is that the 3-blade (smaller blade ratio) is faster with a higher top speed and the 4-blade (higher blade ratio) has a better hole- …

What RPM should I run my outboard?

Most mechanics and engineers suggest the best cruising speeds are achieved at 3400 and 3800 rpm respectively.

What does WOT RPM mean?

wide open throttle
The WOT rating is the RPM range the motor should achieve when running at wide open throttle. If the propeller has too much pitch, the motor will not reach its optimum RPM at WOT, while a prop with too little pitch will exceed the recommended RPM limit at WOT.

Is a higher pitch prop faster?

A prop with too much pitch may deliver more top speed because the prop moves further forward with each rotation, but acceleration may be poor and the boat will struggle to get on plane.

Is it OK to run boat at full throttle?

No it’s not bad on the motor. All outboards are designed for continuous WOT operation. Of course, your fuel economy may suffer! If everything is rigged correctly, I know of no reason why it should be of great concern.

Should you run your boat at full throttle?

Does this mean an engine should never run at wide-open throttle (WOT)? Absolutely not. Modern engines are designed to handle WOT. Also, during break-in going to WOT, as prescribed by the owner’s manual, is necessary to properly seat the pistons’ rings.

How do you know if your outboard is too low?

An outboard that is mounted too low will limit your boat’s optimal operation. You can often tell that an outboard is too low if you are experiencing sluggish speeds, poor handling, excessive spray, porpoising, or even water pushing up into the cowling.

Should I leave my outboard motor up or down?

It’s best to tilt your outboard up when leaving your boat in the water to prevent marine growth from forming and from corrosion eating away at its metal parts.