Boat Prop Basics – Three Questions to Answer Before Shopping for a Boat Prop

The first thing to remember when you are looking for a new boat prop is that there is no single correct boat prop. Typically there will be a number of boat props that will fit your motor. Each different boat prop will have a different performance profile and will give you different benefits. Deciding which boat prop is right for you will depend on your boat and how you use it. The boat prop that might give you maximum speed for running down the lake to your favorite fishing hole might not perform up to your expectations if you were trying to pull a 200 pound wake boarder.

 

Before you start shopping for a new boat prop, you should familiarize yourself with the basic boat prop jargon. We’ve put together an article titled Boat Props Decoded – Understanding Boat Prop Language to give you an overview of the terms you’re likely to run across in researching your boat prop needs. To get started, you’ll need to be able to answer the following questions:

1. What type of engine am I trying to fit?
2. What kind of boat prop do I currently have?
3. Am I satisfied with the performance of my current boat prop?

For the first question you need to have the Make, Model, Horsepower and Year of your outboard or inboard/stern drive combo. This information will be critical to get the right fit for your motor. The same model of motor may change drive shafts from year to year, or different 50 HP models by the same manufacturer may be quite different. Knowing that you have a 1997 BigFoot 60 HP Mercury Outboard will allow you or a sales person to narrow the selections to the boat prop that will work with your engine.

 

Having the answer to the second question, "What kind of boat prop do I currently have?" will allow us to help you replace your existing boat prop if it works fine, or make suggestions if your current boat prop isn’t working up to your expectations. You will want to know how many blades it has (usually 3 or 4), whether its an aluminum or stainless prop, what its diameter is and what the propeller pitch is. The blades and material are pretty easy to determine visually. Aluminum is the most common material for a boat prop and is typically painted or coated. A stainless prop is typically polished metal and will feel heavier and more dense than aluminum. The easiest way to determine the diameter and propeller pitch is to examine your current boat prop. Usually a boat prop will have the diameter and propeller pitch stamped on it, most likely somewhere on the hub. It will typically be displayed as "diameter X pitch." If necessary, you can determine the diameter of your boat prop by measuring the length from the tip of a blade to the center of the hub and multiply that number by 2.

 

The third question "Am I satisfied with the performance of my current boat prop?" will guide you in making the correct selection. If you answer "Yes", then it is a simple matter to select a new prop that matches the existing boat prop you are replacing.

 

If the answer is no, then you’ll need to ask a few more questions and do a little trouble shooting. It might help to think of your boat prop like gears in a car. The size and pitch of a boat prop will influence the operating RPMs of the motor. They will also determine the performance characteristics. When you start out in your car, you’ll start at a low gear that lets you get going easily. When you are cruising down the freeway, you’ll be in a high gear that allows you to go at higher speeds. If you try to start off in 4th gear, you’ll have problems; conversely, if you try to run at 55 mph in first gear you’ll have a serious problem. With a boat prop, you have only the one "gear" so you need to decide which one will best meet your needs. You’ll want to make certain that the boat prop you choose for your boat will allow you to operate in the recommended operating range. Within the selection of boat props that will do that, a higher propeller pitch will allow you to reach maximum top end speeds like a high gear, but you may suffer when getting your boat up on plane or pulling a skier. A lower propeller pitch will give you the quick start and power to get your wakeboarding teenagers up and running quickly, but you may trade some top end speed for that.

 

Watch our Boat Prop Basics YouTube video.

 

Our article The Wide Open Throttle Test - an Important Step in Selecting the Right Boat Prop will show you how to determine if your boat prop is allowing you to operate optimally in the Recommended Operating Range for your motor.

 

 

Learn more about Propeller Pitch, how it affects performance and how to determine the best propeller pitch for your next boat prop.