mjm yachts 50z Downeast, Owner'S Manual

Page: 28 / 72

5.0
5.1
5.2
FUEL SYSTEM
GENERAL
It is important to understand the fuel system aboard your boat. Diesel fuel is different than
gasoline. In most respects it is safer, however precautions need to be taken to maintain the safety
of your boat. Please study the safety precautions in the NMMA publication “Sportfish, Cruisers,
Yachts – Owner’s Manual.”
Diesel engines need to intake more fuel than they burn, and so they differ from gasoline engines
in that they return excess fuel to the tank. Both feed & return of port and starboard engines are to
their respective 260-gallon fuel tanks. The two fuel tanks are connected at the bottom by a
“compensating” fuel line with isolating shut-off valves at both aft inboard corners.
FUEL SHUT-OFF VALVES
These valves are located on top of the fuel tanks aft and are accessed through pilothouse seat
lockers. In the photo of the port tank below the valves for the port tank and the generator are shown
in the open position,.
These valves should be shut down if inspecting a Racor filter, in an emergency
or in case of a fire in the engine compartment.
FILLING THE TANKS
Deck fills are mounted on the side decks, port & starboard, and are labeled “DIESEL.” Each one
services only its respective tank, although with the connecting fuel line valve open, you will get
some transfer to the opposite tank. As the tank is filled, vapor escapes the tank thru the vent.
Care should be taken while filling. Check the fuel level gauges and listen for the
rise in pitch at the deck fill, as fuel reaches the top. Shut off the nozzle
immediately.
Do not attempt to top off” the tanks. Have an absorbent cloth handy
to prevent any overboard spillage. Variations in temperature as well as trim angle
could cause overflow or vent-line blockage.
CHAPTER 5