Aluminum VS Stainless Steel Props: The Differences

Two screw motor boat on the stocks on the beach

If you recently bought a boat that needs a few upgrades or you are looking to improve the performance of a boat you have owned for years, you may be confronted with deciding between installing an aluminum prop or stainless steel propeller. In the propeller industry, these are the two most common options a boat owner can purchase to outfit their boat with, but which is the better choice? This guide will take a look at the various characteristics of both aluminum propellers and stainless steel propellers. Along the way, this guide will look at the life expectancy, cost, advantages, and disadvantages of each type of propeller. However, first it may be necessary to start by exploring the various characteristics that define a boat prop in general. Also just an FYI, a stainless steel prop is also referred to as a ss prop or stainless prop.

A stainless steel prop will give your boat better fuel economy, performance, and is more durable than an aluminum prop. The disadvantage to SS props is their price. An aluminum prop is much cheaper, but is weaker and tends to flex under pressure causing the pitch to change.

General Characteristics of a Boat Propeller

Whether you are looking at a stainless steel or aluminum propeller, you will find three characteristics that define the propeller, its construction, and performance. These three characteristics are the number of blades, the diameter of the propeller, and the propeller pitch. The number of blades a particular propeller is outfitted with varies anywhere from two to five blades. In general, the more blades a propeller has the better it will perform in rough water and accelerating conditions. The diameter of a propeller is measured from one blade tip to the other blade tip that sits reflected over the center of the propeller. In general, a large propeller diameter coincides with better performance and more control over the boat it is propelling. Lastly, the pitch of a propeller will need to match up with the horsepower of your motor as to not overwork your motor. For example, if you have a higher diameter, you may want a lower pitch prop to even it out. Too high of pitch prop can cause cavitation which would be the boat equalizing to burning out in a car. There are tons of guides or dealers to help with that question. That question alone can be the topic of a book.

Aluminum Boat Propellers

Aluminum boat propellers are more plentiful and common than stainless steel propellers. If you happen to damage your current propeller and have to purchase a replacement quickly from a lakeside repair shop, chances are they will have an aluminum propeller in stock. These propellers are more commonly utilized in freshwater situations and provide several advantages. In general, aluminum boat propellers are constructed in several styles sporting 2 to 4 blades, a variety of pitches, and different diameters to support motors with various levels of horsepower. The average cost aluminum boat propeller will run a boat owner anywhere from $100 to $250.

If you don’t need to purchase a new aluminum propeller, and simply need your current prop to be repaired this will cost you anywhere from $50 to $75. Oftentimes, due to the repair price associated with aluminum propellers, it is more advantageous to purchase a new prob and use the hub currently attached to your boat. The life expectancy of an aluminum propeller is quite variable dependent upon care, use, and overall negligence. If you can drive your boat well, then you will be able to make your aluminum propeller last quite a while.

The Advantages of an Aluminum Propeller

Aluminum propellers offer boat owners many advantages. The most common advantages relate to the affordability and easy replacement associated with aluminum propellers. In addition, aluminum props, due to their construction and overall connection to a given boat will actually protect a boat in the event you strike something with your propeller. While damage can still occur to your boat if you strike debris underwater, most of the time with an aluminum propeller it simply damages the propeller itself.

The disadvantages of an Aluminum Propeller

The main disadvantage would be flex of the blades. This will cause the pitch to change at load, which is fine for just tooling around, but if you want the best performance and gas mileage, propeller flex is your enemy.

These blades also are thicker and not as sharp or strong as as stainless steel. This can cause excessive drag which lowers the performance of your boat.

Which Aluminum Props are Best?

Quicksilver makes a great propeller, here is an example of a 4 blade option you can use on your outboard or MerCruiser inboard outboard engine.

Solas also makes a great propeller. Here is an example of a 17″ version.

When choosing an aluminum prop, keep in mind you will need the correct diameter, pitch, and hub style for your engine. A boat service center can help you pick this out, but they are typically cheaper to purchase online.

Here is a handy video on how to pick out a boat propeller whether you want an aluminum or stainless model.

Stainless Steel Boat Propellers

Stainless steel boat propellers are manufactured in all the same styles that aluminum propellers are manufactured. You can purchase a stainless steel propeller with 2-5 blades. However, unlike some aluminum props, almost all stainless steel propellers utilize a hub design. Therefore, it is very common for stainless steel propellers to be outfitted to a particular motor and not interchangeable with other sizes and styles of a motor. The average stainless steel propeller will cost a boat owner between $400 – $1000. These types of propellers, due to their expensive price tag and unique hub connections are less common than standard aluminum propellers.

In the event you damage a stainless steel propeller, you will be able to get it repaired for between $125 to $200. Unlike with aluminum props, it is almost always more advantageous to repair a stainless steel propeller instead of purchasing a brand new one. The life expectancy of a standard stainless steel propeller is much longer. These props are more durable and can withstand some abuse.

A stainless steel prop is better than aluminum if you are looking for the best performance, durability, and gas mileage out of your boat. Their only downside is they tend to cost more than their aluminum counterpart.

The Advantages of a Stainless Steel Propeller

Stainless steel propellers also offer boat owners many advantages. These boat propellers are strong, durable, and constructed in a variety of unique hub and pitch layouts to better mesh with a given motor. If you end up striking something with a stainless steel propeller, chances are your propeller will be just fine. While stainless steel propellers are more costly than their aluminum counterparts, they also lead to better boat performance and increased fuel economy.

Stainless steel props don’t flex under load, therefore the pitch you buy is the pitch you get under load. This will give your boat a better top speed, better mileage, and acceleration. Stainless steel props are also better for abrasive environments.

A stainless steel prop will increase the speed of your boat. In tests, the speed can increase a 3-4 mph on a 150 hp outboard motor. This is significant in the boating world as it will provide better mpg.

The Disadvantages of a Stainless Steel Propeller

The price is the biggest disadvantage. Stainless steel can cost 2-3 times more than thier aluminum counterpart. Also, stainless steel is heavier than aluminum, so you may need more horsepower to push the same size prop.

Which Stainless Steel Props are Best?

Solas makes a good stainless steel upgrade, here is one of their 3 blade models and one of their 4 blade.

Quicksilver is another great brand, here is one of their 3 blade thunderbolt models.

When choosing a prop, keep in mind you will need the correct diameter, pitch, and hub style for your engine. A boat dealer can help you pick this out, but they are typically cheaper to purchase online.

Aluminum Vs. Stainless Steel

The following table takes a direct look at the comparison between aluminum and stainless steel propellers.

More affordableBetter performance
More readily availableBetter fuel economy
LighterMore durable
Affordable as a spareEasier to repair
Doesn’t hold true pitch under loadDesigned for a larger range of motors

Stainless Steel or Aluminum Prop: Final Words

Now that the advantages and disadvantages of both types of propellers have been explored and discussed, it is time to answer the question every boat owner is wondering: which type of propeller is better. The answer is that if you can afford it, you should always go with a stainless steel propeller. These propellers offer better performance and will last longer than an aluminum propeller. If you want to purchase a backup propeller you can always purchase an aluminum one that is less costly. This backup propeller can hold you through in the event you need to have your stainless steel one repaired.

If you are only able to afford an aluminum propeller for your boat, that is fine. It is simply important that you know about aluminum propellers, their performance, and what you can do to improve their lifespan. If you are skilled at driving your boat, an aluminum propeller should last you quite a while. Good luck choosing the perfect propeller for your boat, and have fun out on the water!