The Problem: Your diesel engine overheats shortly after launching. The impeller is brand new.
The Cause: Impeller failure due to an air lock.
The Fix: Although water will displace air in the intake lines when the boat is launched, some air remains in the hose. To prevent premature impeller failure, prime the pump by removing a zinc plug and adding water before starting the engine.
The Problem: There's a faint sooty outline on the salon carpet around the engine hatch.
The Cause: The engine is hungry for more air and is drawing in exhaust fumes.
The Fix: Increase ventilation either with larger exterior vents, a blower system, or both.
The Problem: You observe a faint oil slick in the cooling system's expansion tank.
The Cause: A leak in the oil cooler.
The Fix: Remove the oil cooler and replace the bundles. If the old ones are repairable, have them pressure checked before reinstalling. Oil in the coolant will eventually cause overheating.
The Problem: The transmission housing on your gas inboard is rapidly rusting away.
The Cause: Saltwater is spraying onto the housing from the stuffing box.
The Fix: A stuffing box must drip to cool the packing inside. Secure a short length of exhaust hose around the stuffing box with stainless-steel hose clamps to deflect the spray into the bilge and keep water off the transmission. Better yet, install a dripless stuffing box such as a Shaft Seal (800/523-7558).
The Problem: Your MSD empties slowly.
The Cause: A routine buildup of mineral deposits in the discharge line is restricting the flow.
The Fix: Disconnect the discharge hose and scrape the insides with a coat hanger. Depending upon how much gunk has accumulated, you may be able to salvage the hose. Otherwise, replacement is the best bet.
The Problem: There's a vile sour smell all through the boat.
The Cause: Gray water is leaking into the bilge.
The Fix: Check the shower sump pump reservoir for hair clogging the filter screen, which causes the soapy water to overflow into the bilge. If your boat has a shower and no sump pump, this is your problem. Another likely cause is a leaking hose in the MSD. A concentrated emulsifying bilge cleaner/deodorizer (such as Simple Green Marine) will help sweeten up things.
The Problem: Despite a constant throttle setting, the tachometer is dropping periodically as the engine surges.
The Cause: Most likely, you have a fuel problem.
The Fix: Check the obvious. When did you last change the fuel filters?