BoatHowTo · video

What this video covers

Nigel Calder corrects a common misconception: poor compression in a diesel engine does not cause black exhaust smoke.0:53 Black smoke signals a fuel injection problem — improper fuel delivery or poor atomisation — not a compression failure.1:43 A diesel fires by compressing air until it reaches ignition temperature, then injecting fuel; if compression is adequate, the engine either ignites cleanly or not at all.0:38 The primary sign of inadequate compression is the engine failing to start.Watch How much compression loss triggers that failure depends on ambient air temperature: cold air demands higher compression to reach ignition temperature, so a marginal engine that starts in warm climates may refuse to fire in cold conditions.1:01 Preheaters offset this relationship.1:07 Calder emphasises that compression and temperature interact continuously as an engine wears, and that no single compression threshold guarantees ignition independent of ambient conditions.0:53

More from BoatHowTo

How to keep you TANK CLEAN in the days of BIODIESEL.. | Ask The Expert with NIGEL CALDERAug 2026PARALLELING Conductors for AMPACITY - is that SAFE?? | Ask The Expert with NIGEL CALDERAug 2026ENGINE OIL turns BLACK right after Oil Change?? | Ask The Expert with NIGEL CALDERAug 2026Same LAYUP RECOMMENDATIONS for FAME and HVO bio diesel? | Ask The Expert with NIGEL CALDERAug 2026

From BoatHowTo — see the channel’s boat, crew, and every analysed video.

The Sailing Directory Newsletter

One email with the fleet's best finds — the moments, boats, and stories worth your watch time. Enter your own address to get your own copy.