How to Mount a Small Outboard Motor onto a Catamaran Without Upsetting the Balance
Catamarans do not have one tidy transom in the middle. That makes mounting a motor a little more thoughtful, but not hard. The secret is the bracket, the shaft and the weight.
How to mount a small outboard motor onto a catamaran: fit a strong outboard bracket to the rear crossbeam or a stern, usually on the centreline, choose a long-shaft motor so the prop stays submerged, then clamp, secure and test it with the boat loaded.
Jess, the beach cat and the dead calm
Jess loved her 5 m (16 ft) beach catamaran on breezy days and hated it on still ones. Twice she had drifted for an hour a few hundred metres from the launch point while the sails hung like washing. The second time a passing canoeist offered to tow her, which stung.
A small motor seemed the obvious fix, but the cat had no transom at all: two slim hulls, a trampoline and an aluminium rear beam. Her first idea, clamping to one hull, would have pushed her round in circles and dragged the hull down on one side.
A friend at the club showed her his setup. A sturdy bracket bolted to the middle of the rear beam, a lightweight electric outboard with a long shaft, and the battery stowed forward to keep the sterns from squatting. Jess copied it with a Torqeedo Travel, and now calm days mean a quiet motor home rather than a rescue.
Her verdict: on a catamaran, the bracket and balance matter more than the horsepower.
Where should the motor go on a catamaran?
That depends on the type of catamaran. Here are the usual options.
| Catamaran type | Typical mounting point | Suggested motor |
|---|---|---|
| Beach / sport sailing cat, 4–6 m (13–20 ft) | Bracket on the centre of the rear beam | Light electric or 2.3–4 HP, long shaft |
| Small cruising sailing cat | Stern bracket on the bridgedeck or a dedicated motor well | 4–9.9 HP long shaft, or electric |
| Small power cat with a full-width transom | Centre of the transom like a monohull | 9.9–30 HP to the builder’s limit |
| Twin-hull inflatable or pontoon cat | Centre motor mount supplied by the maker | 2.5–15 HP, matched to the rating |
How do I mount the motor, step by step?
These steps are for a bracket-mounted small outboard on a sailing catamaran. Always follow your bracket and motor manuals.
- Check the ratings. Find the builder’s maximum HP and load, and the bracket’s weight limit. Stay within both.
- Measure the drop. Measure from where the clamp will sit down to the waterline. Most beach cats and sailing cats need a long shaft, about 51 cm (20 in), or a bracket that lowers.
- Fit the bracket. Bolt or clamp it to the rear beam or stern with the fittings supplied, on the centreline, with backing plates where the maker specifies.
- Hang and centre the motor. With the boat secured, lift the motor onto the bracket and tighten both clamp screws firmly.
- Set the depth. With the boat loaded, the anti-ventilation plate should sit just below the surface. Lower the bracket if the prop could lift out in waves.
- Balance the weight. Put batteries, fuel and gear forward and centrally so the sterns do not squat.
- Secure and route. Attach a safety line, route fuel lines or cables clear of the trampoline, rudders and sheets.
- Test at slow speed. Check steering, rudder clearance when turning and that the prop stays submerged when crew move about.
Motors that suit catamarans
Light, long-shaft friendly choices. Prices are starting prices in USD.
- Choose long-shaft versions where offered.
- Electric motors keep beam weight low and split into light parts.
- Add a spare Torqeedo battery for longer range.
Mounting an outboard on a catamaran: FAQ
Can I clamp an outboard to one hull of a catamaran?
It is possible with the right bracket, but a centreline mount is usually better. An offset motor pulls the boat to one side and loads one hull more than the other.
What size outboard does a beach catamaran need?
A light electric or 2.3 to 4 HP petrol motor is usually plenty for getting home in calm conditions. Stay within the boat’s and bracket’s limits.
Do I need a long-shaft outboard for a catamaran?
Usually yes on sailing cats, because the beam or bracket sits high above the water. Measure the drop to the waterline to be sure.
Will the motor get in the way of the rudders?
Check clearance through the full tiller swing and the full motor turn before launching. Many owners lock the outboard straight and steer with the rudders.
No more drifting on calm days.
Send us your catamaran’s make and beam height. We will suggest a motor and shaft that fit.