First MateSimple input, useful results
Enter your speed and fuel level. First Mate estimates engine hours to empty, distance to empty, RPM, fuel burn rate and brake horsepower.
Fuel and range planning for planing powerboats
Know your range before you leave the dock.
Enter your boat once. Then add your speed and fuel, and First Mate estimates hours to empty, distance to empty and engine output for your trip.
Most trip plans start with a manufacturer's rough figure. First Mate starts with your boat: its hull, its engine and the weight you carry today.
First Mate uses naval architecture and marine engineering calculations, built on tow tank test data, to estimate range, duration and engine output. You do not need an expensive integrated management system. The app works alongside the gauges and navigation equipment you already have.
The Dashboard
Two numbers in. A full trip picture out.
Type your cruising speed and remaining fuel. First Mate fills in the rest.
- Hours to emptyAt your current speed
- Distance to emptyFrom head seas to calm
- MPG and GPHEconomy and burn rate
- Engine powerPercent of rated power
- RPM, torque and horsepowerEngine estimates
Screens show example values
Built on naval architecture and tow tank test data, so your plan accounts for drag, weight and engine performance.
Features
Numbers built for your boat, not a brochure average.
Based on naval architecture
Calculations account for drag, weight and engine performance, not just a manufacturer's rough figure.
Set up once
Add your boat in the Vessel tab. Update the specs any time. Print a backup for your logbook.
A dashboard for the trip
Range by speed and weight, engine output, sea state and how it changes your range, plus fluid levels for total displacement.
Reference tables
Trip duration in calm or rough water, remaining fuel from your gauge reading, and sea state on the Beaufort wind scale.
Plan an upgrade
Thinking about a new engine or propeller? See the effect on performance, displacement, range, fuel capacity and horsepower.
How it works
Set up once. Update as you go.
- Vessel tab
Describe your boat
Enter hull, engine and tank specs one time. You can change them any time.
- Dashboard tab
Enter speed and fuel
Add your cruising speed and remaining fuel. Enter new values when conditions change.
- Your Data tab
Fine-tune for your boat
Enter the speed you see at each RPM to match the app to your boat.
Poseidon Vessel Management
One price. Nothing else.
First Mate is made by Poseidon Vessel Management. It is a premium, straightforward app. We rely on word of mouth from boaters, not ads. If you like it, share it with your boating friends.
- No adsNothing gets in the way of your numbers.
- No subscriptions or in-app purchasesPay once and keep every feature.
- No data collectionPoseidon Vessel Management does not collect your personal data.
Results are estimates. First Mate does not read your gauges or connect to your engine.
First Mate · 2026
First Mate in fifteen seconds.
A short look at the app: your range, before you leave the dock.
Available for iPhone and Android
Plan your next run with First Mate.
