PROP PITCH EDUCATION

10% OFF ALL MERCURY STAINLESS PROPS

THE BIGGER THE PITCH THE BETTER RIGHT? WRONG! TOO MUCH PROP PITCH PUTS TO MUCH LOAD ON THE ENGINE.

An engine needs to be able to reach maximum RPM to be correct throughout the RPM range. Like shifting in 4th gear in your car when you should be in 3rd.

Result: Tuliped intake valves, Plug fouling etc.

  • EFFECT OF PROP PITCH ON RPM
    • A pitch change can increase to decrease the RPM's and bring RPM's into the recommended range A 2" INCREASE in pitch (For example from a 21pitch to a 23pitch) Typically results in a DECREASE of approximately 300-400 RPM.
  • FIRST, DETERMINE MANUFACTURES RECOMMENDED RPM
    • Find the manufacture's recommended RPM range in the owner's manual or ask your dealer.
  • TEST FOR MAXIMUM RPM
    • Using the existing propeller or a new propeller, make test runs to determine the maximum RPM and boat speed. Vary the trim angle for optimum performance.
  • RPM HIGHER THAN RECOMMENDED
    • If the actual WOT RPM's are ABOVE the recommended RPM range, install the next LARGER pitch propeller to DECREASE your WOT RPM. Re-test the WOT RPM.
  • RPM LOWER THAN RECOMMENDED
    • If the actual WOT RPM range is BELOW the recommended range, install the next SMALLER pitch propeller to INCREASE your WOT RPM. Re-test the WOT RPM.
  • When you combine all these factors, you have the information you need to select the correct propeller for maximum performance, safety, and fuel efficiency.

JACK PLATE SET UP

The easiest method is to go up until you lose water pressure, gain rpm's and lose speed (all at basically the same time). Then drop the height of the plate 1/2" and it should be perfect. An important thing here is your starting place, here after referred to as Prop To Pad. Three blades need to be started at 3.5" below the pad and four blades need to be started at 3".

The best was to measure prop to pad is to park the boat on a level surface. Then level the trailer. Trim the motor straight up and down----or put a level on the cav plate and level it that way. Take a measurement from the pad to the ground and a measurement from the center of the propshaft to the ground. The difference is your prop to pad measurement. Pad is the area right below the drain plugs and thru hull fittings and you measure from the bottom center of that.

CHINE WALKING

Motor height is the best starting point, if it is too low it will not only cause chine but porpoising as well.  Your prop has to have the correct configuration and cup design to ensure consistent lift and minimal slip.  With the prop and motor height being right, chinning will be a thing of the past.  Always adjust your motor height by water pressure and never get below the recommended pressures for your motor.

PERFORMANCE BASS BOAT SET UP