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What this video covers

Excessive carbon fouling in a Volvo Penta D2-40 exhaust elbow — roughly 50% blockage every 500 hours — is the problem Nigel Calder diagnoses in this Q&A with host Jan Attenstedt.0:29 The owner's 2011 yacht runs at 2,000 rpm against a wide-open-throttle ceiling of 2,700 rpm on what Calder identifies as a 3,000 rpm engine, suggesting the boat is overpropped.1:00 Despite the engine running under load — which should suppress carbon formation — the fouling rate is abnormally high.1:27 Calder outlines three causes in order of cost: first, existing carbon buildup in the exhaust system restricting airflow and compounding incomplete combustion; second, a clogged air filter starving the engine of oxygen; third, one or more injectors failing to atomize fuel properly.1:27 He recommends tracing the full air path from inlet to hull outlet before moving to fuel-system investigation.2:16 A practical field check: open the engine compartment at wide-open throttle and feel for back-pressure, which confirms restricted airflow.2:34 If airflow checks out clean, the problem likely sits in the fuel system and warrants professional diagnosis.2:30

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