Your nose knows when something is amiss. Any changes in the way your boat smells — either when you open it up for the weekend or while running — could mean a problem is developing. Fuel fumes (either gasoline or diesel) must be dealt with right away. Often a leak is caused by vibration of a fuel line against another part of the engine. If this isn’t corrected, it will worsen the breach. If a high-pressure fuel line is leaking, it may be spraying a fine mist of diesel into the air and this could cause a fire.

  • Burning rubber may indicate a slipping belt that can overheat an alternator, or it could indicate freezing bearings in an alternator or water pump that will soon destroy the belt and the component.
  • Steamy water, antifreeze, or overheating paint smells in the engine space indicate an overheating engine. Antifreeze smell may also indicate a breach in the engine’s cooling system, ranging from a burst hose to a cracked head or block.
  • Hot lube oil smell indicates an oil leak, probably requiring immediate shutdown.
  • A burnt oil smell when you pull the dipstick signals a serious internal problem. Have the engine checked immediately.
  • Burning electric insulation smells should never be ignored. It could mean that a terminal is overheating and about to arc and/or short out, or that there is too much of a load somewhere in your electrical system, or that an electrical component is suffering an internal meltdown. Its source must be located immediately. Try to turn off whatever wire or component is involved, preferably at the breaker. It may be a good idea to depower the entire boat, DC and AC, and then turn circuits back on, pausing with each one to see if that’s the cause of the smell.
  • A change in bilge smell, such as a new musty smell, could indicate leaking condensate from the air conditioning or refrigeration units. A leaking shower sump causes its own bad smell.