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Verner Radial Engines

Verner Motor, CZ

Verner Motor is a world leader in the design and manufacturing radial engines for all types of small aircraft. The company specializes in the development and production of drive systems for aircraft in the industry including light sport aircraft, microlight/ ultralight, PPG, powered parachute, trikes and of course historical replica's.

They are also one of the few engine manufacturers which have succeeded in building and selling an authentic looking product for the experimental kit aircraft builder. We are going to take a look at what they have to offer.

Engine Development

Verner started in 1993 with the development of the SVS1400 aircraft engine. This was an opposed piston design and was in production from 1997 until 2000. The company developed and manufactured several engines until they stepped into the radial engine era in 2011. From that moment on, they enjoyed success with the homebuilt aircraft community.

Radial Engines

Verner Scarlett EnginesVerner Scarlett Engines

The first model was the Scarlett mini 3 and mini 5 followed by the Scarlett 7H (production 2014). The Scarlett 7S was introduced in 2015 ending with the 7U/ 9S in 2017 and the Scarlett 3V and 5V in 2018.

Product line

The current Scarlett engine line consist of the 3V/ 5V, 5Si, 7U and 9S series. The table below shows a nice overview of the specifications for comparison:

Engine ModelMax. Output PowerTorqueWeightFuel SystemDisplacement
Scarlett 3V31 kW (42 BHP) @ 2500 RPM123 Nm (90 ft/lb)37 kg (81 lbs)WB37 Carb1635 cc (100 ci)
Scarlett 5V44 kW (60 BHP) @ 2300 RPM181 Nm (133 ft/lb)54 kg (119 lbs)WB37 Carb2725 cc (166 ci)
Scarlett 5Si61 kW (85 BHP) @ 2300 RPM296 Nm (218 ft/lb)69 kg (152 lbs)EFI3390 cc (207 ci)
Scarlett 7U91 kW (124 BHP) @ 2300 RPM390 Nm (287 ft/lb)83 kg (182 lbs)EFI4740 cc (290 ci)
Scarlett 9S116 kW (158 BHP) @ 2300 RPM485 Nm (357 ft/lb)108 kg (238 lbs)EFI6094 cc (372 ci)

The number in the designation denotes the amount of cylinders: 5Si means a five (5) cylinder engine.


The engines have a magnesium crankcase with aluminum cylinders and cylinder heads, the basic TBO is 1000 hours (600 for the three cylinder models) and increasing as the fleet builds hours. The recommended fuel is Mogas 95 octane (compression ratio 1:7.8) and is either fed with a carburetor or with a fuel injection system. None of the engines have a reduction drive so a huge propeller can be used with this engine providing lots of thrust.

Electrical, Oil

The electrical system consists of a 12 V alternator of 336 W, the starter is 12 V / 1 kW. The engines uses spark plugs from Denso type Q20PR-U. Lubrication oil is sourced from AeroShell with 15W50 viscosity and sits in a separate oil tank with gravity return.

A detailed explanation of the Scarlett 9S can be seen in the next video from ScaleBirds USA.

Company information

Verner can be contacted at the addresses below:

Verner Motor
Vikýřovice 562
788 13 Šumperk, Czech Republic
+420 602 595 739 (mobile)
[email protected]

Text and images used with permission (pending) of Verner Motor.

Written by EAI.

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