# Propeller Shaft Torque Calc — Marine Shaft Size & Speed

> Marine Shaft Size & Speed (iPhone/iPad app by Shanghai Sheyuan Network Technology Co., Ltd..)

- Source: https://appshunter.io/ios/app/propeller-shaft-torque-calc/id6761676394 (this page in markdown: same URL + `.md`)
- Developer: [Shanghai Sheyuan Network Technology Co., Ltd.](https://appshunter.io/developer/1560626858)
- Category: Utilities, Productivity
- Price: $1.99
- Age rating: 4+
- Requires: iOS 17.0 · 1 MB
- Languages: American English
- Released: 2026-04-08
- Data updated: 2026-07-19
- User reviews in markdown: https://appshunter.io/ios/app/propeller-shaft-torque-calc/id6761676394/reviews.md

## What is Propeller Shaft Torque Calc?

Repowering your boat and need to know if the existing shaft can handle more torque? Enter engine HP, RPM, and gear ratio to get required shaft diameter, torsional stress, and critical speed margin — so you avoid a broken shaft at sea.

TORQUE CALCULATOR
Enter engine horsepower, shaft RPM, and safety factor. Calculates required shaft torque, minimum shaft diameter, and torsional stress. Supports multiple shaft materials.

SHAFT SIZE TABLE
Reference table of common shaft diameters (3/4 to 4 inches) with maximum torque capacity for stainless steel and Monel. Includes recommended RPM ranges for each size.

MATERIAL COMPARISON
Compare marine shaft materials: 316 Stainless, Monel K-500, Aquamet 17, and Aquamet 22. Shows yield strength, fatigue limit, corrosion resistance, and typical applications side by side.

CRITICAL SPEED
Calculate critical shaft speed based on shaft length, diameter, and bearing spacing. Shows safety margin above operating RPM to avoid vibration resonance.

Built for marine engineers, boat builders, and propulsion system designers. Works offline.


## Version history (last 3 releases)

### 1.0.2 — 2026-07-07

Added a More Pro Tools section to discover related field calculators.

### 1.0.1 — 2026-04-13

Bug fixes and performance improvements.

### 1.0 — 2026-04-08

No release notes.

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All apps by Shanghai Sheyuan Network Technology Co., Ltd.: https://appshunter.io/developer/1560626858

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-07-19.*