Wightlink Ltd v Mitchell Diesel Ltd (t/a Mitchell Power Systems)

A technical manual supplied by a manufacturer is not incorporated into a contract merely because the parties use it as a reference document. Whether incorporation has occurred depends on the parties’ intention and whether the relevant document is apt to form part of the contract.

A contractor may discharge its contractual duty of reasonable skill and care by adopting a technically justified practice which departs from recommended manual tolerances, provided there are sufficient engineering reasons for doing so. Loss must still be causally established. Necessary betterment arising from reasonable repairs is not deductible from damages.

Wightlink engaged Mitchell Diesel Ltd to overhaul the engines of two high-speed passenger ferries. After several engines suffered failures or required inspection, Wightlink claimed the costs of removal, repair and storage, alleging that the defendant had improperly machined piston-pin bushes and had otherwise breached its contractual duties.

The principal issues were whether the manufacturer’s manual formed part of the contracts, whether the defendant’s machining practice breached the duty of reasonable skill and care, whether that practice caused the failures, and whether the repair costs were reasonable or represented betterment.

1. Contractual scope. The overhaul contracts did not expressly incorporate the manufacturer’s manual, and no such incorporation could be inferred. The manual was drafted as a guide to inspection and repair, not as a contractual specification. Its flexible provisions and the bespoke nature of the work made it unsuitable for strict contractual incorporation. The approach in Alexander & Ors v Standard Telephones and Cables Ltd (No 2) [1991] IRLR 286 was applied.
2. MPS nevertheless owed contractual duties to exercise reasonable skill and care and to ensure that replaced or reconditioned components were satisfactory and fit for use. The manual was the obvious and relevant reference point, including its recommended tolerances, but strict compliance was not required.
3. Causation. Wightlink failed to prove that the smaller piston-pin clearances caused the engine failures or other defects. The court preferred the defendant’s expert evidence. The proposed mechanism was technically unsubstantiated, inconsistent with the physical evidence and unsupported by comparable documented examples. The likely cause was overloading of the lubricating-oil system, but its precise cause was not proved.
4. Breach. Selective machining was technically justified and consistent with accepted engineering practice. Although MPS should have considered the manual’s recommendations and should not have departed from them without good reason, sufficient reasons existed here. The machining therefore did not breach the contractual duty. A possible separate issue concerning consultation with the manufacturer was not decided because it had not been pleaded or properly explored.
5. The secondary alleged breaches were either unproved or causally irrelevant. One breach concerning wrongly located relief valves was established, but no resulting loss was proved.
6. Quantum. The repair costs were reasonable. Necessary betterment resulting from repairs did not reduce the recoverable loss, applying Bacon v Cooper (Metals) Ltd [1982] 1 All ER 397. Wightlink’s failure to carry out an earlier service did not break the chain of causation.
7. The claim was dismissed.