About Diesel and Marine Group

About Diesel and Marine Group

Diesel and Marine Group is comprised of Simplex-Turbulo Co Ltd, based in Wherwell, Hampshire; as well as Lincoln Diesels Ltd; and the brands Dorman Diesels and Durability Coatings.

We aim to supply high quality components (wherever possible directly from original component manufacturers) and to cut delivery times to the minimum by constant investment in stock.

Our goal is to keep our customers’ engines and vessels working at maximum efficiency and with minimum downtime. Our strategy for achieving this is to: 

  • develop close relationships with our customers so that we can work together to ensure repairs and dry dockings are carried out seamlessly and fast.
  • invest heavily in stock, and in computer systems, in order to cut down delivery times and enable us to offer better value.
  • cultivate our technical expertise, training our own engineers and liaising with the research departments of our suppliers.
  • constantly reassess the quality both of the components we supply (to ensure longer time between overhaul) and of the service we provide. We aim, at all times, to be professional and honest with our customers.

Simplex-Turbulo Company

In addition to its traditional marine components, Simplex-Turbulo provides service and spares suitable for* Bergen, Wärtsilä, Nohab Polar, Stork and MaK diesel and gas engines.

Lincoln Diesels

Lincoln Diesels provides service and spares suitable for* Mirrlees Blackstone, Ruston, Ruston & Hornsby, Paxman, WH Allen, MAN B&W, Sulzer, Perkins and Pielstick diesel engines, as well as providing a full reconditioning service for major components, including a service exchange scheme.

Dorman Diesels

We own the brand Dorman Diesels. Also based in Lincoln, they support Dorman diesel engines with new or reconditioned spare parts and servicing.

Durability Coatings

Specialist coatings service for marine, mining and other industries which suffer from abrasion, cavitation or corrosion. Typical applications include propeller blades, thrusters, ventilators, and pump impellers. Suitable for new equipment or restoring worn items.

History of S-T Diesel and Marine Group

‘Simplex Rudder & Turbulo Auxiliaries Ltd’ was originally founded in 1935. In 1956, the name was changed to Simplex-Turbulo Marine Company Ltd, and in 1985, the name of the company was changed once again to Simplex-Turbulo Company Ltd, which it remains today. The company is family owned, but SKF Marine have a substantial minority shareholding. With the decline of British shipbuilding, the company diversified its product range within the marine and diesel sectors, and achieved its first sale with the installation of the Simplex balanced rudder for the Castle Combe in 1936. This rudder was so well balanced it could be operated by hand. From 1948, much of the sales activity was focused on the Simplex sterntube seal and the Turbulo bilge water separator. In 2004 it bought the company Lincoln Diesels Ltd. In 2010, the brand Dorman Diesels also joined the group. In 2013, the group acquired the brand Durability Coatings and began offering high velocity oxygen fuel coating techniques.

The group employs 60 members of staff, and exports globally to over 50 countries. Approximately £5m worth of diesel and gas engine components stock is held in our stores.


The first recorded sale of Simplex equipment was a balanced rudder for the “Castle Combe”, 23rd September 1936

Group T/O

  • Turnover (£m)
  • Group operating profit (£m)
  • Net assets (£m)

Year end: 30th September


Group T/O£13.60m£14.30m£15.16m
Group operating profit£1.34m£1.70m£1.70m
Net assets£3.40m£3.80m£4.15m
Turnover splitUK £5.50m 38%

Other EU £3.30m 24%

ROW £5.50m 38%
UK £5.51 36%

Other EU £3.30m 24%

ROW £6.04m 40%
Accounts basis UK GAAP
Auditors Crowe Clark Whitehall LLP in Reading UK
Bankers HSBC Bank plc


James Hogg

James Hogg

James Hogg is Chairman of the S-T Diesel & Marine Group. He has an MA in Jurisprudence from Oxford University, and an MBA from London Business School.

Clare Hogg

Clare Hogg is Director of Marketing and HR for the S-T Diesel & Marine Group. She’s a language graduate; has a MA Marketing; is a Chartered Marketer; a Fellow of the Chartered Institute of Personnel and Development; and an Institute of Directors Accredited Director.

Justin Brooking

Justin Brooking is Director of Finance and Resources at S-T Diesel & Marine Group. He has a B Eng and is ACMA qualified.

Andreas Thiele

Andreas Thiele completed an engineering apprenticeship in Germany and has subsequently been working in industrial engineering management ever since. Currently he is Director of Business Development at SKF Blohm + Voss Industries. He is a qualified Dip. Wirt. Ing.


Employees (Total Group)
60 employees based in Andover, Lincoln, Newcastle, and Szczecin in Poland

Diesel and Marine Group

Our environmental policy

Simplex-Turbulo Group Ltd (STG) is an agent and distributor for engineering components and machinery covering a wide range of industries.  The company recognises that these products may have an impact on the environment during their manufacture and use and is committed to minimising their impact throughout their life cycle by pursuing best environmental practice whenever and wherever practicable.  In addition STG also offers service work and this service work is organised so to minimise possible damage to the environment through leakage and inefficiency.

  The company will therefore:

  • Screen all products and suppliers thoroughly to ensure the components minimise damage to the environment.
  • Adopt a ‘cradle to grave’ assessment of and responsibility for, our components and services.
  • Meet all legislative requirements and, wherever possible, go beyond these requirements.
  • Ensure staff are trained to understand the Policy and have the skills and knowledge to implement it
  • Adopt an environmentally sound transport strategy
  • Give technical feedback to suppliers to facilitate design for optimal performance.
  • Ensure all subcontractors operate in line with the principles of our environmental policy.
  • Record and analyse any environmental pollution so as to minimise the impact and prevent a future occurrence.

In line with these principles, STG has sourced its heat requirements from a wood pellet boiler using renewable fuel, and established the following objectives:

  • To reduce waste and energy usage at source
  • To give technical feedback on the design of components so that new components will minimise their environmental impact
  • To service and repair existing components so as to reduce damage to the environment
  • To provide advice to all our customers to ensure the safe use of components

*If you are operating your engine under the parameter system, please let us know so that we can discuss your requirement.