Marine automobile engine

Volkswagen Marine 3.0 litre V6 TDI 265-6 marine engine. This is a marine-modified version of Volkswagen Groups 3.0 V6 24v TDI CR automobile engine.

Marine automobile engines are types of automobile petrol- or diesel engines that have been specifically modified for use in the marine environment. The differences include changes made for the operating in a marine environment, safety, performance, and for regulatory^[1] requirements. The act of modifying is called 'marinisation'.^{[citation needed]}

All of the "Big 3" American auto companies have had engines marinised at some point. Chrysler is notable, because the company marinised engines in-house through Chrysler Marine, as well as selling engines to third parties such as Indmar or Pleasurecraft Marine.

General Motors marine automobile engines are based on a gasoline truck engine. That means four-bolt main bearing caps instead of just two; sometimes the crankshaft is forged steel and the pistons an upgraded aluminum alloy. Most importantly the camshaft profile is different with the overlap ground to 112 degrees instead of 110. Expansion plugs are bronze to better fight corrosion. The head gasket's metal O-ring is also more corrosion resistant. ^[2]

Safety modifications

Electrical systems^[3]

• Marine starter motor — it has an internal screen to minimize the egression of spark movements.
• Marine alternator differs from an automobile alternator — it has an internal screen to minimize the egression of spark movements.

Fuel systems (petrol/gasoline engines)^[4][5]

• Fuel pump vented — if the fuel pump diaphragm ruptures, then the excess fuel will be directed into the carburettor. This kind of fuel pump is referred to as a marine fuel pump.^[6]
• Marine carburettor does not allow the overflow into the boat engine compartment.^[7]
• Spark arrestor on the air intake (carburettor or electronic fuel injection) — a wire mesh screen on the spark arrestor cools any internal flame or spark created by back-fire, thereby preventing it from igniting fuel vapours inside the engine compartment.^[8]

Fuel systems (diesel engines)

Cooling systems

• Marine automobile engines are water-cooled; drawing raw water in from a pickup underneath the boat. In an open cooling configuration, the raw water is circulated directly through the engine and exits after passing through jackets around the exhaust manifolds. In a closed cooling configuration anti-freeze circulates through the engine and raw water is pumped into a heat exchanger. In both cases hot water is released into the exhaust system and blown out with the engine exhaust gasses.
• The transmission oil cooler is cooled by raw water.

Performance modifications

• The marine distributor does not have a vacuum advance. Vacuum advance is normally actuated at high engine revolutions per minute (rpm) in low load situations - and this situation generally does not occur in the marine environment. Under normal operation, high rpm generally means high engine load.

References

External links

• Boatbuilder's Handbook Downloads from the U.S. Coast Guard
• Marine Diesel Engines from Volkswagen Marine