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Common Questions About Boat Propellers

by: smiparts( 19193Feedback score is 10,000 to 24,999) Top 5000 Reviewer
288 out of 302 people found this guide helpful.
Guide viewed: 13678 times Tags: boat prop | prop | propeller | outboard prop | mercury prop


What are some common signs that it may be time for a new propeller?

Your boat takes longer to get on plane than it used to. It uses more fuel. It doesn’t seem to run as fast as it did when it was new. If your boat feels sluggish, one of the first things you should check is your propeller. Is it showing signs of wear and tear? Does it have more than its share of nicks, dings and missing paint? These symptoms can accumulate and significantly impair the performance of a perfectly good engine.

What is Pitch?

Pitch is the theoretical distance, in inches, that a propeller moves forward during one revolution. Think of a screw as you turn a screwdriver once around. The distance that the screw travels into the wood is the pitch. Propeller size is specified in inches of pitch.

How do I know what pitch is right for me?

Consult the engine owner’s manual to find the recommended wide-open-throttle (WOT) range for your engine. If the current propeller is at WOT RPM within the specified RPM range, select a replacement or upgrade propeller with the same pitch as the current propeller.

If the current propeller isn’t at WOT RPM within the recommended RPM range, select a replacement or upgrade propeller with a larger or smaller pitch using the following rules:

  • Adding 1 inch of propeller pitch will reduce WOT RPM by 150 to 200. 
  • Subtracting 1 inch of propeller pitch will increase WOT by 150 to 200.
  • If you’re upgrading from a three blade to a four blade propeller, remember that a four blade propeller generally turns 50 to 100 RPM less than a three blade prop with the same pitch

Stainless Steel vs. Aluminum

It’s a question of strength and performance.  Aluminum propellers usually cost quite a bit less, however, stainless steel is over five times more durable than aluminum. If you’re looking for quicker acceleration, superior top speed, or better overall performance, you should consider a stainless steel propeller

Three- vs. Four-blades

Four blade propellers usually:

  • Plane the boat faster than 3-blade propellers
  • Keep the boat on plane at a lower speed
  • Give improved mid-range speed at the same RPM as a 3-blade propeller
  • Provide quicker acceleration than most 3-blade propellers
  • Run smoother than 3-blade propellers
  • Have better holding power in rough conditions
  • Are less likely to ventilate in sharp turns
  • Provide better low speed handling
  • Are not quite as fast on the top end as a comparable 3-blade propeller

Please feel free to contact us for information on props or to help you select the correct prop for your application

The following information is needed to assist in the selection of a prop:

  • Boat Mfg, Year, Make and length:
  • Engine MFG, Year, Make and horsepower:
  • Current prop Mfg, pitch, and type (Stainless, Aluminum, 3 blade, 4 blade
  • Current WOT RPM
  • Performance requirements (quicker plane, top speed, etc)

Guide ID: 10000000000016801Guide created: 10/07/05 (updated 10/12/08)

 
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