Prop School

or call 952-937-9173

Prop Rotation

Is your prop Left Hand or Right Hand rotation?

When looking at the prop from the back of the boat:

When a boat has twin engines, the left hand rotation prop will be on the Port side of the boat and the right hand prop will be on the Starboard side of the boat.

Left Hand props are, by far, the most common for V drive wake boats.

Pitch

Pitch is measured in inches, the theoretical distance that is traveled in one rotation of a prop assuming that there is no slip. The dimensions of a prop are always written in this format: Diameter x Pitch where the diameter is first and the pitch is second.
Increasing pitch will decrease RPMs and theoretically increase top speed, assuming there is enough horsepower available to turn the prop.
Another way to look at this, if speed is constant, such as when; wake surfing, skiing, etc, increasing pitch will decrease RPMs at those speeds.  You need to be careful to keep your RPMs in a desirable range so that you are running efficiently and not bogging down your motor. 
Decreasing pitch will increase RPMs at surf speed which will increase low end power, which is beneficial in producing wake or pulling people out of the water.  On the top end, decreasing pitch will reduce top speed.


How to Prop your boat

Surfing
Surf speed is typically 10-12 mph
RPM's at surf speed should be between 3000 - 3500

A variety of variables can affect what your RPM is at surf speed
      • Ballast
      • Surf gates and/or wedges
      • Number of people in the boat
      • Elevation
      • Water/air temperature

Pitch

If your RPM's are below 3000, then you should decrease your pitch

If your RPM's are above 3500, then you should increase your pitch

Diameter

Typically you want to maximize your prop diameter on a wake boat while leaving a minimum of 1" of clearance between the prop blades and the boat hull

Cupping

Usually used to make very minor changes to dial in a prop.  At higher elevations, over 4k feet, we often recommend to have a lower cup

Prop Repair

If you damage your prop, it can usually be repaired however they can sometimes be beyond repair if it is missing too much material or if the bend is too deep in the prop (bent at the root).

When selecting a shop to do your repair, it is important that they have the correct pitch block for your prop.  We have pitch blocks for every variation of prop that we sell, which puts our pitch block count over 600. 

If a shop attempts to repair your prop without the right pitch block, they will change the geometry of your prop and it will; have different performance, could have vibration, may be impossible to repair the next time because the prop no longer matches any block.   We frequently get props from customers that need a re-repair due to vibration caused by a bad repair at another shop.

Prop Sing

This is referred to a humming noise that can come from a prop.  The singing is caused by the harmonics of the prop caused by the water leaving the trailing edge of the prop.  The noise typically is limited to a narrow RPM band and goes away.  This noise is not causing any damage to your boat or the prop but it is annoying and can easily be fixed.

Prop Sing is not common and it can happen on new props right out of the box or a fresh repaired prop.  The fix to prop sing only takes 1 minute in the shop and we always do this repair for no charge, whether the prop was purchased or repaired through us or not.

 

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