How to LS swap a boat: parts list and steps

A boat LS swap has to solve marine-specific cooling and exhaust, and mate the engine to your drive (outdrive, V-drive or jet).

What a real build used (LSX Magazine, a Gen III LM4 replacing a 489 big-block in a boat):

• a mostly stock LS bottom end with upgraded bearings, forged pistons and a BTR cam;
• a Holley 750 CFM marine carburetor on a dual-plane intake;
• a Holley/MSD LS ignition controller, since the carburetor setup doesn't use a factory LS computer;
• a high-torque starter and a Melling oil pump and timing set.

Exhaust is the hard part: LSX Magazine found no economical LS boat headers on the market, and their first set turned out to point the wrong way.

Marine suppliers stock LS-specific parts: Hardin Marine sells LS accessory drive kits, cams, engine mounts, exhaust systems, flywheels and power take-offs, and outdrive/jet/V-drive components.

Plan the drive coupling, cooling system and exhaust first, then the engine.