diesel engine maintenance and powerboat seamanship 157
Check the freshwater cooling system (before start-up). Many engines
have an externally mounted expansion tank that collects freshwater coolant
as it circulates through the engine. Make sure the expansion tank coolant
level stays within a half inch of the full mark (or at the level indicated by your
manual). Next, check the engine coolant level through the oblong-shaped heat
exchanger header tank on top of the engine. Aft er making sure the header tank
is cool to the touch, remove the radiator pressure cap on top of the tank and
stick a fi nger in. Keep the coolant level within a half inch of the top. Also check
the freshwater cooling hoses.
Check the radiator pressure cap (before start-up). Little things turn
into big problems. Before putting the pressure cap back onto the header tank,
turn it over and check the gasket seal. Worn seals lead to fluid leaks. Replace
the entire pressure cap if you have a bad seal.
Check the drive belt (before start-up). Th e belts on the front of your
engine drive the shaft , alternator, and freshwater pump. Th ey stretch over time
and may develop cracks on top and bottom. No belt should have more than
a half inch of play when depressed with moderate fi ngertip pressure. Check
your manual. Most belt adjustments are made by moving the alternator along
its mounting bracket. Loosen the bolt and wedge a large screwdriver between
the alternator and engine block. Lift up on the alternator. Adjust or replace the
belt and retighten the bolt.
Check the stuffi ng box (before start-up, while underway, and aft er shut-
ting down). Th e stuffi ng box forms a seal where the shaft exits the hull. With
the shaft turning, a drop of water every 20 to 30 seconds (1 or 2 drops every
minute) isn’t cause for concern. Th is helps keep the shaft cool and lubricated.
Excessive leaking indicates loose, worn, or missing packing material. First,
try tightening the packing nuts on the shaft. You will need two oversized
wrenches to accomplish this task. Aft er tightening, restart the engine and
check the leak drip rate again. If it’s still excessive, you’ll need to replace the
packing inside the stuffi ng box. Do not use the engine until you address this
problem. Always check the stuffi ng box before you leave the boat. Many boats
sink at the dock or at anchor because this fi nal, all-important inspection was
neglected. (In Chapter 13, we’ll look at strategies for dealing with fl ooding
and other emergencies.)
Check the exhaust (after start-up). Bend over the transom or stern
quarter to make sure there is a healthy fl ow of cooling water coming out of
the exhaust. If the cooling water output is absent or restricted, your engine is
not getting enough seawater, and you should shut it down. If the raw-water
seacock, strainer, hoses, and belt are normal, the most likely problem is an
obstruction (say, a plastic bag or seaweed) blocking the raw-water intake
strainer on the outside of the hull. To check this, close the raw-water seacock,