Download over 500 Boat PlansDownload Now

Gear Ratio Calculator

Calculate the optimal gear ratio for your boat's propulsion system

Quick Samples
Try these common configurations to get started

High-RPM Outboard

Typical performance outboard setup

Standard Inboard Diesel

Common diesel cruiser setup

Trawler / Tug

Low-speed, high-torque application

Hull Dimensions
Enter your boat's principal dimensions
Download 500+ Boat Plans
About This Tool
This calculator estimates the ideal marine gear ratio by considering the engine's max RPM, the desired top speed, and the propeller's pitch. It helps in matching a transmission to an engine and propeller for optimal performance.

Key Concepts:

Gear Ratio: The reduction in speed from the engine to the propeller.
Propeller RPM: The speed the propeller must turn to achieve the target boat speed.
Propeller Slip: The inefficiency of the propeller in water.
Tip Speed: The speed of the propeller blade tips, a factor in cavitation.
Frequently Asked Questions

Download 500+ Boat Plans
Get access to a comprehensive library of boat plans and tutorials.

"My Boat Plans" is a collection of over 500 boat plans, from simple dinghies to larger cruisers. It includes step-by-step guides, video tutorials, and more.

Download Now