Marine automobile engine

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Marine automobile engines are automobile engines that have been modified for the marine environment. The differences include changes made for safety and for performance.

[edit] Safety

Spark arrestor on the inlet of the carburettor. This prevents flames inside the carburettor from exiting into the engine compartment.
Fuel pump vented to the spark arrestor. If the fuel pump diaphragm ruptures, then the excess fuel will be directed into the carborator. This kind of fuel pump is referred to as a marine fuel pump.
Screen on the distributor. This prevents spark from exiting the distributor and igniting any fuel vapor which may be in the engine compartment. This kind of distributor is referred to as a marine distributor.
Sealed carburettor. The external vents present on an automobile carburettor are sealed at the factory. This kind of carburettor is referred to as a marine carburettor.
Water jacketed exhaust. The exhaust manifold in a covered engine compartment is surrounded by water to prevent exposure of a hot surface on which fuel vapor may ignite. Water pumped from outside the boat is usually used for the exhaust manifold. Passing the water through the manifold first also serves to preheat the water before it is used to cool the rest of the engine.

[edit] Performance

No vacuum advance. Vacuum advance is normally engaged at high RPM low load situations, which don't happen in the marine environment. Under normal operation, high RPM means high engine load.