Yanmar 1GM10 Diesel Engine Repair

I need an experienced mechanic to fix a Yanmar 1GM10 diesel engine that won't start. The engine shows no warning lights or error codes.

Ideal skills and experience:
- Expertise in diesel engine repair, particularly Yanmar engines
- Strong troubleshooting skills
- Familiarity with marine engines and systems
- Ability to work in South Essex area

Please provide a detailed assessment and repair plan.