The engine is part of the boat. Every serious cruising sailor uses it — and the ones who pretend otherwise either have perfect wind every day or take twice as long to get anywhere. These guides cover how to motor well, when to motorsail, and how to plan a passage around fuel reality rather than optimism.
When to Motorsail (and Why You Should)
Most cruising boats motor 25–40% of any passage. Understanding when to put the mainsail up while motoring — and drop the guilt — makes every voyage faster and safer.
- Optimal at 40–150° apparent wind
- Mainsail adds 0.5–1kt over engine alone
- Light air, head seas, schedule pressure
Motoring Technique: Running Your Diesel Well
The RPM range, instrument checks, fuel burn rates, and the engine check routine that prevents the overheated engine 60 miles from port.
- Cruise at 60–75% of max RPM
- Check instruments every 30 min
- 0.4–0.8 L/hr typical auxiliary burn
Motorsailing Upwind: When the Engine and Mainsail Work Together
The physics of combining the engine and mainsail against a head sea — optimal angles, sail configuration, and when motoring into the wind actually beats sailing.
- Best at 40–60° apparent wind
- Headsail partially furled upwind
- Managing lee helm under power
Fuel Range Planning for Passages
The 75% rule, consumption benchmarks for common auxiliaries, range calculations, jerrycan management, and finding diesel in places that make you nervous about the quality.
- Range = tank × 0.75 ÷ L/hr
- 20hp burns ~1.0 L/hr, 40hp ~2.0 L/hr
- Always plan the no-engine contingency
About These Guides
These guides cover general principles for typical auxiliary diesel sailboats in the 28–50 ft range. Engine specifications, fuel burn, and performance vary by boat, propeller, and conditions. Always verify fuel consumption figures against your own engine's manual and your logged hours. For marina fuel docks and services, see the marina directory.