Trevessa IV PZ 193

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We carried out a largescale upgrade and optimisation project on the Trevessa IV, the first stage in an ongoing programme to enhance the W Stevenson & Sons’ 12-strong fleet. The  dual objectives were to increase fuel efficiency and maximise the vessel’s performance, as well as improving crew comfort and safety.

We started by carrying out a wholesale review of the Trevessa’s existing performance, including its stern gear arrangement and underwater hull design, in order to identify the optimum vessel design and replacement engine and gearbox combination.

We selected a Caterpillar C32A  electronically controlled engine, with its Wide Operating Speed Range (WOSR), for improved fuel and propulsion efficiency, and a Masson gearbox. We also fitted a new hydraulic pump onto the gearbox PTO and a new CJC fuel filtration system, and as a result the vessel is now 20 per cent more fuel efficient.

Given the complexity of this project, we began planning well in advance of the 10 April 2017 start date, to allow plenty of time for the new gearbox to be manufactured and delivered. We removed the existing engine and gearbox by cutting a hole in the ship’s cabin and then installed a brand new assembly, produced using advanced 3D design.

We lifted off the deckhouse, including galley and crew quarters, in one piece, allowing us to refurbish them simultaneously with the engine refurbishment.

Working with Parkol was a pleasurable experience as they were always willing to listen and act on any suggestions we put forward.  

Most importantly, the changes were immediately apparent when we took Trevessa IV out to sea for engine and fishing trials, when the boat felt good, performed well and was noticeably faster from the moment we left the pier ends.

Skipper Robert ‘Fish’ McCreath


W Stevenson & Sons Ltd
Home Port: Newlyn, Cornwall

Completed: May 2017

Technical Specification
Hull Material:
Main Engine:
Caterpillar C32A
Auxiliary Engine:
Mitsubishi 6D16
Masson MMW7400 RCA 9.077:1 reduction
Nozzle Diameter:
Length OA:
Beam MLD:
Moulded Depth:
13.4 knots
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