Propane (LPG) outboards promise easy starts, no stale gasoline and no carburetor gumming, using the same fuel many sailors already carry for the galley stove. They have a loyal following among dinghy and small-sailboat owners, but they also come with real trade-offs in model choice, fuel range and safety handling.

Quick answer: a propane outboard makes sense if you run a small motor (around 2.5–6 hp) occasionally, hate fuel-system problems after lay-ups, and already carry propane safely on deck. It makes less sense if you need more power, long range, very cold-weather starting, or easy dealer support, because the choice of models is small and some brands have left the market.

How a Propane Outboard Works

A propane outboard is essentially a small four-stroke gasoline engine with a different fuel system. Instead of a carburetor, it uses a pressure regulator and a fuel mixer. Propane leaves the tank as a vapor under its own pressure, so there is no fuel pump, no float bowl and no priming bulb. A shut-off valve stops the flow when the engine is not running.

Fuel comes either from a small 1 lb camping cylinder (on some models it fits under or beside the cowling) or from a larger external tank connected by a hose. Propane has a high octane rating (above 100), and because it enters the engine as a dry gas it does not wash oil off the cylinder walls the way liquid gasoline can.

Which Propane Outboards Are Available?

The market has always been small, and it has shrunk. Before buying new or used, check what is actually in stock and supported in your country.

Tohatsu 5 hp LPG

Tohatsu’s propane 5 hp is based on its single-cylinder 123 cc four-stroke. It has forward, neutral and reverse, a fuel shut-off valve, and comes in standard and sail-oriented versions with a high-thrust prop in some markets. Weight is around 60 lb, only slightly more than the gasoline version. US retailers quote roughly five hours at full throttle from an 11 lb tank. It is the most widely available propane outboard today, but stock varies by region.

Mercury 5 hp Propane

Mercury sold a 5 hp propane FourStroke built on the same 123 cc platform, including a long-shaft Sail Power version. Some dealers still list it while others show it as unavailable, so treat it as “check current availability” rather than a sure thing.

Lehr 2.5 and 5 hp

Lehr popularized propane outboards in the 2010s with 2.5 hp and 5 hp models that ran from a 1 lb canister clipped to the motor. The company is no longer producing outboards, and owners on boating forums report difficulty finding parts and support. A used Lehr can still be a cheap, light dinghy motor, but buy one only if it runs well and you accept that spares may be hard to find.

Pros of Propane Outboards

• No stale fuel or ethanol issues. Propane does not go off in storage, does not absorb water and does not leave varnish in a carburetor. For motors that sit idle for weeks, this is the biggest advantage.
• Easy starting. There is no priming or flooding, and most users report starts in one or two pulls once the system is pressurized.
• No winterizing the fuel system. You still need to look after the lower unit, cooling system and oil, but there is no carburetor to drain.
• Cleaner and less smelly. No spilled gasoline, no fumes in the cockpit locker, and lower exhaust emissions than older carbureted engines.
• One fuel on board. If your galley stove and grill already use propane, you can carry a single fuel type (with suitable fittings and storage).
• Easy refills in many places. Exchange tanks and camping cylinders are sold widely, although marina fuel docks rarely sell propane.

Cons of Propane Outboards

• Limited choice. Essentially only around 5 hp and below, from very few manufacturers. If you need 8–9.9 hp to push a larger sailboat, propane is not an option.
• Range and fuel monitoring. A 1 lb cylinder lasts only around an hour at moderate throttle (less at full power). It is hard to see how much is left; weighing the tank is the most reliable method.
• Cold weather. Propane pressure drops as temperatures fall, and small cylinders can frost up and lose pressure during long runs. Performance in near-freezing conditions can suffer.
• Less energy per gallon. Propane carries roughly a quarter less energy per gallon than gasoline, so you burn more volume for the same work. Any cost savings depend on local propane and gasoline prices.
• Service and parts. Many outboard mechanics rarely see propane units, and the regulator and mixer are specific parts. Discontinued brands are a particular risk.
• Safety handling. Propane is heavier than air and must never be allowed to collect in a bilge or cabin (see below).

Propane vs Gasoline vs Electric

	Propane	Gasoline four-stroke	Electric
Power range	Small (around 2.5–5 hp)	Wide (2.5 hp and up)	Small to medium
Fuel storage	Doesn’t degrade	Degrades; ethanol issues	Battery, needs charging
Range	Limited by tank size	Good with external tank	Limited by battery
Refuelling	Exchange or refill tanks	Any fuel dock	Shore power, solar, generator
Maintenance	Low fuel-system upkeep	Carburetor care needed	Very low
Model choice / support	Very limited	Excellent	Growing

If your main goal is avoiding fuel problems on a dinghy or small sailboat, an electric outboard is now the main alternative to propane. If you need range and power, a modern gasoline four-stroke remains the practical choice. Our guide to the best outboard motor brands compares the main makers, and what size outboard you need for a sailboat will help you decide whether 5 hp is enough.

Propane Safety on a Boat

Propane is safe when handled properly, but the rules are strict because the gas is heavier than air. A leak below deck can pool in the bilge and ignite from a spark.

• Store propane tanks on deck or in a dedicated, sealed locker that drains overboard. Never store tanks, full or “empty”, in the cabin or bilge.
• Use hoses and fittings designed for the motor and the tank, and inspect them regularly for cracks and chafe.
• Close the tank valve when the motor is not in use, even though the engine has its own shut-off valve.
• Check connections for leaks with soapy water, never with a flame.
• If you smell gas, shut the tank valve, stop the engine, ventilate and do not operate electrical switches until the smell is gone.
• Keep a fire extinguisher accessible. See our list of must-have boat safety equipment.

Refilling 1 lb camping cylinders from a larger tank is common, but those cylinders are generally sold as disposable, and refilling or transporting refilled cylinders may be restricted. Follow local rules and the manufacturer’s guidance.

Is a Propane Outboard Right for You?

A propane outboard is a good fit if you:

• Need 5 hp or less for a tender, small daysailer or trailer sailer
• Use the motor occasionally and want to avoid carburetor problems
• Already carry propane safely and can refill or exchange tanks easily

Look elsewhere if you need more power, long motoring range, reliable cold-weather operation or easy access to parts and service. Whatever you choose, keep up regular care; our article on common outboard motor problems covers the basics that apply to any small four-stroke.

Summary

Propane outboards solve the most common small-outboard headache, stale gasoline, and they start easily and run cleanly. In exchange you get a very limited choice of motors (mainly around 5 hp), shorter range per tank, weaker cold-weather performance and patchier support, with Lehr no longer making outboards. Tohatsu’s 5 hp LPG is the most available option today. Store propane on deck, check connections and plan your fuel, and a propane outboard can be a clean, low-fuss choice for a small boat.