On a crisp winter morning at Greenhithe, the True Kit team launched two boats: the Discovery 330 and the Discovery 400. Our goal? To answer the questions every owner asks about True Kit performance - from engine setup to propellers, weight balance, and take-off techniques.
This on-water session wasn’t just about speed; it was about teaching how small, smart adjustments can make your True Kit inflatable catamaran perform at its absolute best.
Choosing the Right Outboard Motor
When it comes to outboards, there’s something for everyone. Some boaters prefer smaller, lighter engines for portability, while others opt for higher horsepower for power and speed.
True Kit boats comfortably handle motors from 2 hp (and electric) up to 20 hp (Depending on the model). The balance lies in choosing what matters most to you - weight, power, or fuel economy.
- 2-stroke engines: lighter and punchy, though increasingly rare due to emissions restrictions.
- 4-stroke engines: cleaner, more efficient, and now standard in most countries.
And let’s not forget the growing appeal of electric outboards. Brands like ePropulsion, Torqeedo, Remigo and Mercury are redefining small-boat power with lightweight, rechargeable, and whisper-quiet performance - a perfect fit for True Kit owners who value convenience and sustainability.
All True Kit inflatable boats are designed for short-shaft outboards, ensuring the propeller sits at the ideal depth for efficiency and reduced drag. You can run a long shaft, but it will sit deeper in the water, creating extra resistance and trimming a few knots off your top speed.
Outboard Shaft Length Explained
The right shaft length determines how smoothly your motor transfers power to the water.
A short shaft keeps the propeller at the correct height, maintaining clean water flow. Too long, and the prop runs too deep, wasting energy on drag and turbulence. For every True Kit model - from the Navigator 2.5 m up to the Discovery 4 m - a short shaft is the best choice for balanced, fuel-efficient boating.
Propellers – The Unsung Heroes of Performance
Every outboard relies on its propeller to turn horsepower into forward motion, and not all props are created equal.
Key elements to understand:
- Diameter – total width from tip to tip.
- Pitch – how far the prop would move in one revolution through solid water.
- Cupping – the rolled edge that helps the prop “bite” into the water.
- Rake – how the blades angle forward or backward.
- Blade area – larger blades usually mean more grip and lift for lightweight catamarans.
Key propeller design features that match well with True Kit boats are:
- Larger blade area - typically the props are so smaller that any increase in area is a benefit
- Extra cupping (the curled lip on the trailing edge of the blade) - gains extra “grip” on the water as the prop is turning - particularly noticeable when accelerating, cornering or in choppy conditions.
- More Rake - reduces ventilation and raises the bow (you just need to counter the bow rise with weight forward)
- Lower pitch if the boat is heavily loaded, higher pitch if high speed on a lightly loaded boat is the goal
Material matters too. Aluminium props are durable and cost-effective, while stainless steel versions are stiffer, thinner, and deliver higher-end performance for those chasing every bit of efficiency.
Fine-Tuning with Engine Trim
Your engine trim controls how the outboard sits in the water and directly affects how your boat rides. Most engines feature a trim pin with multiple holes, allowing you to alter the angle.
- Pin in lowest hole: Engine tucked under - lowers the bow for faster planing. Often best for one person in the boat as they are down the back holding the outboard tiller arm.
- Pin further back: lifts the bow for smoother cruising in chop and helps keep the boat level as you load the boat with more passengers towards the front.
True Kit generally recommends the lowest trim setting for rapid take-off and balanced performance, but the perfect setup depends on your load and water conditions. A small tweak here can make a huge difference in how smoothly your boat planes.
Hydrofoils and Permatrims – The Secret Boosters
If there’s one accessory that consistently improves inflatable catamaran performance, it’s a hydrofoil - and Permatrim is True Kit’s preferred option.
Hydrofoils work by expanding the surface area of your cavitation plate, which:
- Stops air being sucked down around the prop (preventing ventilation).
- Increases water pressure for stronger grip.
- Forces more thrust horizontally, helping keep the bow down.
This results in faster take-off, better stability, and smoother cruising - particularly with heavier loads or smaller engines.
You can find a range of performance-enhancing accessories in the True Kit Accessories Collection.
Take-Off Tips for Smooth Acceleration
A common mistake is to slam the throttle open from standstill. Instead, think of taking off on a wet road - if you floor it, you’ll just spin your tyres.
The same applies on water. Gradually apply throttle so the propeller keeps full grip. This technique dramatically improves acceleration, reduces fuel use, and minimises wear on your engine. Smooth equals fast.
Understanding True Kit Transoms
The transom is your boat’s power bridge - where the outboard meets the hull. True Kit transoms are marine-grade aluminium, making them incredibly strong yet lightweight.
Each model features a customised transom height to match its intended motor size:
- Discovery 4 m: higher transom to support 15–20 hp four-strokes.
- Navigator 2.5–3 m: slightly lower transom for smaller engines and lighter loads.
This precise engineering ensures efficient power transfer and keeps your propeller at the correct depth for optimum thrust. Most people would be quite surprised at how much power can be lost if a transom is not a very rigid structure for this power transfer. Don’t settle for removable transoms!
Weight Distribution – The Key to a Level, Fast Boat
As the team likes to say, “a level boat is a fast boat.” Weight distribution makes or breaks your performance.
Key principles:
- Single operator: sit as far forward as possible - use a tiller extension to steer comfortably.
- Two people: helm aft, passenger forward on opposite side.
- Three people: helm in centre seat, others forward on either side.
- Four people: two aft on tubes, two forward on tubes for even balance.
Also, secure the fuel tank forward in the bow. This simple change can transform how quickly your True Kit jumps onto the plane.
Planing Capabilities in Action
The True Kit demonstration showed impressive real-world results:
- Discovery 4 m + 15 hp: easily reached 30 km/h with two people.
- Three adults onboard: maintained steady planing speed.
- Four people: still responsive, stable, and efficient.
- Discovery 330 + 8 hp two-stroke: clocked 27 km/h, proving how lightweight hulls deliver big performance from small engines.
The takeaway? With proper setup, even modest power delivers thrilling, effortless rides.
Cavitation and Ventilation Explained
Understanding these two phenomena is essential for maintaining performance and protecting your gear.
- Cavitation happens when steam bubbles form on the low-pressure side of the propeller - usually from improper pitch. It feels like vibration through the hull.
- Ventilation occurs when air reaches the propeller blades, causing sudden over-revving and loss of thrust.
How to prevent them:
- Use cupped or large-blade props.
- Keep the boat level and balanced.
- Fit a Permatrim hydrofoil.
These adjustments ensure your prop grips properly and your True Kit remains smooth, fast, and reliable.
Perfecting Your True Kit Setup
After a morning of testing, one message was clear: fine-tuning your setup pays off. From choosing the right outboard and propeller to trimming, balancing, and adding a Permatrim, every tweak enhances performance.
True Kit inflatable catamarans already combine lightweight design, stability, and low drag - the perfect foundation for small outboards or electric power. When dialed in, they deliver an effortlessly fast, efficient, and exhilarating boating experience.
Testimonial from a lifetime boatie:
I followed the team’s email and video advice and put the engine angle all the way down, added a long tiller, and placed myself just behind the forward seat to run the Discovery 330 with the Tohatsu 15hp with the cupped prop and Permatrim. I am glad I did not change to the older style boat. Everything ran beautifully. Zero cavitation or prop slip, and ran at 19 knots/22 mph/35kph. Bounced over too many waves with flawless performance.
So, I eat my words! The advice seemed counterintuitive to everything I had learned from developing Deep Vs and larger cats over the past 30+ years…..but it worked! Peter Johnstone
