diesel engine maintenance and powerboat seamanship 161
body. Black streak marks indicate a worn gasket. Keep an eye on this when
underway. If it worsens, call a mechanic and ask him to replace the head
gasket or check for more serious problems. Coolant leaks oft en result from
loose caps or worn gaskets on the cap. Th is is no diff erent than a leak from
the cap on your car’s radiator. You have to have a good seal or the fl uid leaks
from the top. Press down on the cap and tighten it. If it still leaks, the cap
gasket may be worn, preventing a proper seal. Replace the cap before you use
the engine.Fuel System Maintenance
Replace primary fuel fi lter(s) (as needed). Locate the primary fuel fi lter. Th e
top contains a basketlike fi lter. Aft er many hours of use, the basket fi lter gets
clogged and loses its trapping ability. Open the top cover, then pull out the
fi lter element and gasket. Replace the element and gasket at the same time.
When you change the fuel fi lter, air gets into the fuel lines. You must bleed all
of the air from the system in order to start the engine. Each engine is diff erent,
so follow the process shown in your engine manual. Consider installing two
primary separator fi lters right aft er the fuel tank. Dual fi lters allow you to keep
the engine running while changing one fi lter at a time.
Replace the secondary fuel fi lter (as needed or at specifi ed intervals). It’s
easy to forget the secondary fi lter, because it’s oft en hidden on the side of the
engine block. Follow your engine manual for the recommended fi lter change
frequency. If the secondary fi lter is dirty, the primary fi lter is almost certainly
dirty as well (though the converse is not necessarily true). And if the second-
ary fi lter is dirty and your fuel system includes an electric or manual lift pump
between the primary and secondary fi lters, you should check the fi lter screen
in the lift pump as well.
Replace the deck fi ll cap gasket (as needed). Keep your deck fi ll cap
tightened and change out the gasket annually. Before fueling, make sure to
surround the fi ll with absorbent pads, and wrap a rag or pad next to the nozzle
body. Wipe off the deck fi ll cap threads before screwing the cap back down.
Hire an expert for 2 hours. If you’ve never worked with injectors or fuel
systems, ask a mechanic to do the job. What if your engine runs like a top?
Hire a mechanic for 2 hours once a year. Get him to look things over, make
recommendations, and show you something new. The time and money are
well spent.
THE AIR SYSTEM
Engines require great quantities of air to operate efficiently. The intake system
needs fi ltration to keep dirt and dust out. Th e exhaust system must provide an
unrestricted path to remove extreme heat and engine gases.