Automotive and Marine Parts – How Different Are They?

In a recent episode of Car Masters: Rust to Riches, the Gotham Garage crew reconstructs a marine engine to function in a Mad-Max style Volkswagen bus. This overhaul required the complete rebuild of the bus frame, and automotive system to make it fully operational. The vehicle is coined, the Frank N’ Bus, and for good reason. Automotive parts and marine parts are suited specifically to their environment and can only be used interchangeably with substantial changes to systems and structure design. Let’s take a look at why.

The main differences between marine engine parts and automotive parts are in the placement of the engine itself. Marine engines, unlike automotive engines, are entirely enclosed. This leaves them more vulnerable to combustion and corrosion. Air cannot rush around the engine in a marine environment, unlike cars, whose engines are always partially exposed. This seemingly simple factor leads to integral differences in parts and regulation.

Take, for example, one of the most well recognized automotive devices, the carburetor. Both marine vessels and automotive vehicles require a carburetor in their engine. However, as you may know, a carburetor discharges overflow (unmixed fuel), that sometimes drips out of the device. In an automotive vehicle, this excess material can be expelled onto the ground.

The aforementioned is not the case in a marine engine. The contained nature of a marine engine makes overflow or vapor from a carburetor extremely hazardous. To safeguard against this, marine engines are equipped with vents to allow the excess material to be filtered back to the engine. A marine carburetor must be protected by an air filter as well, but one made of metal mesh. In a car, the carburetor is usually protected by an air filter made of plastic.

Another excellent example of the differences between the two environments, are the starter and alternator. In a marine version of these components, they are required to be ignition protected. This involves the installment of vents with flame arrestors and complete containment of the units to prevent corrosion. In an automotive engine, there is less risk with high voltage sparks. Automotive starters and alternators have exposed contacts that allow for air cooling and ventilation.

The distributor also varies considerably in both engines. The function of a distributor in both engines, speaking rudimentarily, is the same— its main purpose is to channel voltage to spark plugs in a spark-ignition combustion engine. This mechanism can emit high voltage sparks as well and requires protection similar to that of the starter and alternator. In a marine engine, yet again differentiating from an automotive environment, the distributor is completely sealed to limit corrosion, and is equipped with a vent and flame arrestors.

Both engines differ in mechanics and design. Due to the fragile environment of marine engines, they are also more highly regulated on an industry wide basis. Marine engines and fuel tanks must meet standards set by the U.S. Coast Guard and the American Boat & Yacht Council. So, while it is tempting to test out the compatibility of both engine parts, we recommend you’re prepared to do a complete rebuild vis-a-vis Gotham Garage before you make that venture. 

1. john symond
2. Posted on March 6, 2019
aviation

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