# Propeller Calc vs YDIS Smart

The clearest difference is review sentiment: Propeller Calc at 100% against YDIS Smart's 43%. YDIS Smart's advantage is rating (3.7 vs 3.0) and update cadence (every 3 months vs every 21 months). On price, ads, in-app purchases and monetization model there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

YDIS Smart holds the better App Store score, 3.7 against 3.0. That said, the two scores are not equally well evidenced: YDIS Smart has 16 ratings behind it against 1, so its average is the more settled of the two. Written reviews complicate that: 100% of Propeller Calc's written reviews are positive against 43% of YDIS Smart's, so the app with the better star average is not the one people write more warmly about.

Propeller Calc ships an update every 21 months, YDIS Smart every 3 months. The most recent releases landed on September 9, 2026 and September 16, 2026 respectively.

## The numbers

| Metric | Propeller Calc | YDIS Smart |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.0 (1 ratings)](https://appshunter.io/ios/app/propeller-calc/id478119478/reviews) | **[3.7 (16 ratings)](https://appshunter.io/ios/app/ydis-smart/id1062728896/reviews)** |
| Number of ratings | 1 | **16** |
| Positive reviews | **100.0% of reviews** | 42.9% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 21 months | **Every 3 months** |
| Monetization | Free | Free |
| Size | 3 MB | 7 MB |
| Requires iOS | 17.0 | **12.0** |
| Devices | iPhone, iPad | iPhone, iPod |
| Age rating | 4+ | 17+ |
| Developer | [Frode Rørvik](https://appshunter.io/developer/478119481) | [Yamaha Motor Co., Ltd.](https://appshunter.io/developer/337268490) |

## What reviewers say

### Propeller Calc

[App page](https://appshunter.io/ios/app/propeller-calc/id478119478)

This utility calculates propeller performance metrics like pitch, gear ratio, RPM, slip, and speed. Input any four values, and the app computes the fifth, helping users understand the relationship between propeller design and boat performance.

**Highlights:** Calculate pitch, gear ratio, RPM, slip, and speed, Enter any four variables to find the fifth, Understand propeller slip and its impact, Supports iPhone and iPad, Free to use

**Features:** macOS Compatibility

**In-app purchases:** none


### YDIS Smart

[App page](https://appshunter.io/ios/app/ydis-smart/id1062728896)

This application allows authorized Yamaha dealers to access diagnostic functions for Yamaha outboard motors on their smartphones. It requires a dedicated adapter and registration information for the PC version of the diagnostic system.

**Highlights:** Perform inspections of Yamaha outboard motors, Access self-diagnostic system functions, Use on smartphones, Requires dedicated adapter, Requires YDIS PC version registration, Enable speedometer display with GPS

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Propeller Calc free?

Propeller Calc is free to download, with no in-app purchases.

### Is YDIS Smart free?

YDIS Smart is free to download, with no in-app purchases.

### Which has better reviews, Propeller Calc or YDIS Smart?

YDIS Smart is rated higher. Propeller Calc averages 3.0 out of 5 from 1 ratings, while YDIS Smart averages 3.7 from 16 ratings.

### Do Propeller Calc or YDIS Smart have ads?

Neither Propeller Calc nor YDIS Smart shows ads.

### Which is updated more often, Propeller Calc or YDIS Smart?

Propeller Calc ships an update every 21 months, and YDIS Smart every 3 months. Most recently, Propeller Calc was updated on September 9, 2026 and YDIS Smart on September 16, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*