Todd Scruggs isn’t just keeping a 1982 Peterbilt 359 on the road—he’s rewriting the rulebook on what these old-school rigs can do. By yanking the original engine and dropping in a 700-horsepower CAT C18 marine diesel, he’s built one of the most aggressive, torque-rich logging trucks we’ve seen. But this isn’t just a flex piece—this Peterbilt hauls real loads, does real work, and has the scars to prove it.
In this walkaround, Todd explains how a tugboat engine ended up powering a long-nose Pete through the tough hills of Tennessee. This rig doesn’t just sound mean—it’s a legit engineering feat, with mods to cooling, gearing, and power delivery that make it practical for day-to-day timber hauls. Whether you’re into off-road recovery, big torque builds, or just love old iron that’s still earning its keep, this one’s for you.
CAT C18 Marine Engine Swap
Let’s get into the meat of it. The CAT C18 used here isn’t your average heavy-duty truck engine—it’s a marine-rated beast originally built to push tugboats through the water. With 700 horsepower and mountains of low-end torque, it’s capable of towing just about anything on wheels (or off).
What makes this swap special is how Todd adapted the engine to fit a 1982 Peterbilt frame. That meant:
- Custom motor mounts and frame mods,
- Serious cooling upgrades (big radiator, external oil coolers),
- A reworked intake and exhaust system to manage marine-style airflow in a land-based application.
Marine engines are built for constant load at low RPM, so adapting one to highway and off-road hauling takes finesse. And yet—it works like a dream.
Gearing – Drivetrain & Performance
Power means nothing without control. That’s why this build pairs the CAT C18 with an 18-speed transmission—crucial for putting down power without shredding the drivetrain. The gearing allows Todd to finesse the truck’s torque delivery, especially when hauling logs up steep grades or maneuvering through soft ground.
The 359’s rear ends were reinforced to handle the engine’s torque, and the clutch system was upgraded to cope with marine-level grunt. The result? A truck that doesn’t just pull—it climbs and hauls like few others in its class.
Real-World Use: Hauling & Reliability
This isn’t a show truck—it’s a working rig for Scruggs Timberland Services. That means reliability is just as important as horsepower. Todd talks about the challenges of daily driving a custom build like this: monitoring temperatures, balancing fuel economy, and keeping vibration and stress under control with smart preventive maintenance.
Unlike many custom builds, this Peterbilt is designed to be repaired in the field if needed. Standard parts were used where possible, and the marine engine has proven surprisingly durable—logging thousands of miles with minimal issues, even under full load.
If you’re into engine swaps that make sense—and make power—this one sets a new bar. Would you daily drive a 700-hp marine rig? Let us know in the comments.