RC Outboard Motors: Electric, Scale and Gas Outboards for Model Boats
An RC outboard is a complete drive unit that clamps to the boat’s transom: motor on top, a leg with a gear or flexible drive down to the propeller, and the whole unit pivots for steering, so no rudder is needed. Electric gear-drive outboards with brushless motors (for example a 3660-size 2070 kV unit for boats under 1 m) are the most common; scale outboard kits look like real Mercury racing engines; and gas outboards power large tunnel boats. Here’s how they work, how to size one and how to fit it.
By Kyle HilsonUpdated: October 20264 min read
Types of RC outboards
| Type | Drive | Typical boat | Notes |
|---|---|---|---|
| Electric gear-drive outboard | Brushless motor on top, bevel gears in the lower unit | Tunnel boats, F1-style hulls, scale runabouts under about 1 m | Compact, water-cooled; example: 3660 2070 kV, up to about 29 V and 60 A |
| Electric flex-cable outboard | Motor on the leg or in the boat, flexible cable to the prop | Racing tunnels and hydros | Simple, efficient; cable needs greasing |
| Scale outboard kits (e.g. 1:8 Mercury Racing styles) | Hidden brushless motor in a scale cowling | Scale powerboats and F1 boats above about 70 cm | Looks like the real engine; some take motors up to 4076 size |
| Gas outboard | Small petrol engine (often 26 cc class) | Large tunnel and sport boats | Loud, long runs; needs a pull start and tuning |
| Toy outboard units | Small brushed motor and plastic prop | Bath toys, kids’ boats | Simple fun, not hobby grade |
Examples from retailer listings, checked October 2026; specific models change frequently.
Why choose an outboard?
- Steering without a rudder: the whole thrust line turns, giving sharp turns at speed.
- No hull drilling: no stuffing tube or shaft hole, so fewer leaks.
- Easy swap and trim: tilt (trim) the leg to change how the boat rides.
- Scale look on runabouts and racing tunnels.
- Downside: weight sits at the very back; small boats can get tail-heavy.
How to size an outboard
| Boat length | Electric outboard | Battery |
|---|---|---|
| Up to about 60 cm | Small outboard with 28–30 mm brushless motor | 2S–3S |
| 60–100 cm | 36 mm-class motor (e.g. 3660) gear drive | 3S–6S |
| Over 1 m | 40 mm-class motor or twin outboards; gas outboard | 6S+ or 26 cc gas |
Typical pairings; always check the outboard’s maximum voltage and current and use a water-cooled marine ESC rated above it. Motor theory for boats: model boat electric motors.
Fitting and setting up an outboard
- Reinforce the transom with plywood; outboards put a lot of leverage on it.
- Mount at a height where the anti-cavitation plate sits roughly level with the hull bottom; adjust in small steps.
- Connect a strong waterproof servo to the steering arm with a short, stiff linkage.
- Route cooling water from the outboard’s pickup through ESC and motor jackets, and out through the hull side.
- Set trim: tilt the leg out (trim up) for more speed on calm water, in (trim down) for control in chop.
- Check the propeller direction and use the recommended prop; too big a prop overheats the system.
Electronics and waterproofing steps are in how to wire an RC boat.
Maintenance
- Grease the gears or flex cable as the manual says; dry running destroys them quickly.
- Rinse after use, especially in salt or dirty water, and dry the lower unit.
- Check the prop for nicks and the drive pin or nut for tightness.
- Flush the cooling lines and look for blockages.
FAQ
Can I put an outboard on any RC boat?
On most flat-transom hulls, yes, with a reinforced transom. Boats designed for inboard drives may need re-balancing.
Are RC outboards steerable?
Yes, the whole unit pivots via a servo, which replaces the rudder.
Is there a static scale outboard for display?
Yes, scale outboard model kits exist for display or to hide a motor inside; check whether a kit is static or drivable.
Gas or electric outboard?
Electric for most boats: simpler, cleaner and powerful. Gas outboards suit large boats and long runs.
More on this topic: the complete RC Boats guide covers the basics behind this article.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
