How to Find the Size of a Boat Prop: A Comprehensive Guide for Marine Professionals

Finding the size of a boat propeller involves identifying two key dimensions: diameter and pitch. The diameter is the width of the circle formed by the propeller blades, while the pitch is the distance the propeller would move in one revolution. This information is typically stamped or engraved on the propeller. For example, a marking like ‘9.25 x 8’ indicates a diameter of 9.25 inches and a pitch of 8 inches. Brands like Honda, Mercury Marine, and Yamaha have unique ways of displaying this information, often on the hub or blade of the propeller. It’s essential to record this information when the prop is new for easy reference during replacements.

Understanding the size of a boat propeller is not just a matter of routine maintenance; it’s a critical aspect of ensuring optimal performance and safety in marine operations. It’s best to find this information when the prop is brand new… write it down and put it away somewhere safe. This article delves into the nuances of identifying prop sizes, focusing on prop diameter and pitch, across various brands. It’s tailored for professionals in the marine industry, offering detailed insights and practical tips to keep you well-informed and your vessels in top condition.

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Understanding Propeller Size

The size of a boat propeller is a crucial factor that affects the boat’s performance. It includes two main dimensions: the diameter and the pitch. The diameter is the width of the circle that the propeller blades make as they rotate, while the pitch refers to the distance the propeller would move in one revolution if it were moving through a soft solid, like a screw through wood. Each propeller has their own location and sometimes information that’s available. This section will guide you through the general method of identifying prop sizes, ensuring you have the knowledge to make informed decisions about your boat’s propeller.

Identifying Prop Size by Brand

Different brands have unique ways of marking their propellers, and understanding these can save time and effort, especially when replacements are needed. Let’s explore how various brands mark their propellers:

Honda Propellers

Honda typically uses a combination of stamped and engraved numbers on their aluminum props. For instance, a prop marked “9.25 times eight” indicates a nine and a quarter inch diameter prop with an eight-inch pitch. 1420… are some type of internal reference that Honda maybe even a batch number.

Evinrude/Johnson Propellers

Evinrude and Johnson props often have their size information on the outside, with part numbers like “10.3 x 13.” This is actually a 10 and a quarter inch diameter prop, highlighting the need to understand brand-specific nuances.

Solas Propellers

Solas opts for clear markings on the outer part of the hub. A prop marked “13.3 and then 17” would mean a diameter of 13.3 inches (or 13.25 inches) and a pitch of 17 inches. Those two numbers represent the dimensions like we saw on the previous two props.

Mercury Marine/Quicksilver Propellers

Mercury Marine and Quicksilver have a unique approach, stamping or casting the size into the outer part of the hub. However, they actually cast it into the inner part of the hub as well, which can be easier to read but covered up when the prop is installed.

Suzuki Propellers

Suzuki engraves the size on the outside of the hub, using a straightforward system without part numbers. For example, “3x 16 20” would mean a three-blade propeller with a 16-inch diameter and a 20-inch pitch. The added ‘R’ indicates standard right-hand rotation.

Yamaha Propellers

Yamaha often hides their size information inside the hub, making it accessible only when the prop is removed from the drive. Yamaha tends to hide theirs away… the only way you can find this information is to actually remove it off of the drive itself.

Importance of Early Identification

It’s crucial to record your propeller’s size information early in its life. As the prop ages, numbers can wear away or become hard to access. The most important part is to go ahead and do this early when the prop is new. This proactive approach ensures that when it’s time for a replacement, you’re not left guessing.

Knowing your boat propeller’s size is more than a technicality; it’s a fundamental aspect of marine craft maintenance. By understanding the specifics of prop diameter and pitch, especially as they vary across brands, you can ensure your vessel operates at its best. Remember when it comes time to replace your prop, you already have your information ready to go.

Merrill Charette

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