BoatHowTo · video

What this video covers

A 35-year-old Universal M18 diesel engine fails to reach its rated 3200 RPM, topping out at 2700 RPM in neutral while stalling at low idle and producing black soot on the transom.0:14 Despite replacing injectors, fuel filters, and oil, and verifying compression is within specifications, the engine performance remains degraded.0:38 Nigel Calder suggests checking for hidden fuel restrictions, specifically a fouled filter screen on the fuel tank pickup tube, a clogged check valve on the primary fuel filter inlet, or a plugged filter screen inside the lift pump.1:37 If fuel delivery is confirmed, the mechanical governor may be fouled with internal sludge, preventing the flyweights from operating against the spring tension.3:09 Because the injection pump is expensive to service and requires precise retiming, inspecting the governor mechanism for stiffness or debris serves as a critical intermediate troubleshooting step.3:37 Black smoke and poor RPM response indicate a fuel-air ratio imbalance often caused by restricted flow or governor failure.

More from BoatHowTo

Boat ELECTRIC PROPULSION with only LEAD ACID Batteries ?? | Ask The Expert with NIGEL CALDERSep 2026MaxProp: More Pitch in Reverse than in Forward? 🤔 | Ask The Expert with NIGEL CALDERSep 2026Common Ground Point with Isolated Saildrives | Ask The Expert with NIGEL CALDERSep 2026How to keep you TANK CLEAN in the days of BIODIESEL.. | Ask The Expert with NIGEL CALDERAug 2026

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