Technically, you might be able to bolt a marine carburetor onto a car engine, but it is an extremely dangerous and ill-advised modification. The core reason is safety: marine carburetors are engineered for a completely different environment and lack critical safety features required for automotive use. Installing one on a car creates a significant fire and explosion hazard.
The primary difference lies in the carburetor's design to handle fuel vapors. In a boat's engine compartment, which is enclosed, any leaked gasoline vapors can accumulate and become trapped. To prevent an explosion, marine carburetors are fully sealed and equipped with special flame arrestors on the intake to extinguish any potential backfires. Automotive carburetors, in contrast, are designed to allow these vapors to dissipate safely in the open-air environment under a car's hood. Using a marine carburetor on a car can cause it to run excessively rich or lean, leading to poor performance, stalling, and engine damage.
Beyond the severe safety risk, the modification is often impractical. Linkages for throttle and choke may not align with automotive setups, and the carburetor's calibration (jetting) is specifically for marine engines, which often operate at higher, steady RPMs. This makes for terrible drivability in a car, which requires a wide power band for acceleration and cruising. You would also likely void your insurance and fail any safety inspection. The small cost saving is never worth the risk.
