The Yanmar 6LPA-STP is one of the most widely respected mechanical-injection diesel engines ever installed in mid-size cruising and sportfishing boats.
Commonly found in vessels like the Mainship 30, Albin 28 Tournament Express, Back Cove 29/30, and similar semi-displacement or planing hulls, the 6LPA earned its reputation through a combination of compact size, high horsepower for its weight, fuel efficiency, and long-term reliability.
It also became a favorite for repowering older boats, thanks to its relatively straightforward mechanical systems and strong performance in the 28–32 foot range.
Key Facts & Specifications: Yanmar 6LPA-STP / 6LPA-STP2
General Specifications (typical):
- Engine Type: Inline 6-cylinder, 4-stroke marine diesel
- Aspiration: Turbocharged
- Fuel System: Mechanical fuel injection
- Rated Power:
- 6LPA-STP: approx. 315 HP
- 6LPA-STP2: approx. 315–350 HP (depending on rating year)
- RPM at Rated Power: ~3,800 RPM
- Displacement: ~4.2 liters (4,164 cc)
- Configuration: Compact footprint suitable for tight engine rooms
- Typical Application: Single-engine installations in 28–32 ft cruisers or twins in light commercial craft
Transmissions
Frequently paired with: Frequently paired with Kanzaki / Yanmar marine gears with models such as KMH or equivalent. Straight or down-angle configuration with ratios often in the 2:1–3:1 range.
Cooling System
Freshwater-cooled heat exchanger system. Oil coolers and gear coolers typically plumbed into the raw-water circuit. Designed for warm-water operation common in our Gulf Coast climate.
Vessels Commonly Powered by the Yanmar 6LPA
You’ll routinely see the 6LPA-STP in single-engine Downeast & Express Cruisers, such as:
- Mainship 30 Pilot / Sedan
- Albin 28 Tournament Express
- Back Cove 29 / 30
- Eastern 27 / 28
- Legacy 28
These boats benefit from the 6LPA’s:
- Ability to cruise economically in the high teens to low-20-knot range
- Torque curve
- Single-engine efficiency
Why the 6LPA Became So Popular for Repowers
The 6LPA hit a sweet spot when gasoline inboards and early diesels were being phased out:
- Excellent power-to-weight ratio for its era
- Compact size relative to output
- Broad dealer network and parts availability
- Proven track record in thousands of installations
For owners of older Mainships, Albins, and express cruisers originally powered by Crusader, MerCruiser, or Perkins gasoline engines, the Yanmar 6LPA offered:
Diesel efficiency, longevity, and resale value without an overly complicated electronic control package.
Maintenance and Support
One reason the Yanmar 6LPA-STP and 6LPA-STP2 remain so sought after on the brokerage market is their long-term serviceability. Routine maintenance follows classic diesel best practices—regular oil and filter changes, valve adjustments at scheduled intervals, aftercooler and heat-exchanger servicing, injector inspections, and vigilant raw-water pump upkeep. Because these engines rely on mechanical fuel injection rather than complex electronic control systems, many owners appreciate the ability to diagnose issues more easily and keep them running reliably with proper preventative care. Yanmar’s long presence in the marine market also means parts availability and technician familiarity remain strong across most coastal regions.
Conclusion
The Yanmar 6LPA-STP carved out its reputation by delivering big-engine performance in a compact, efficient, and durable package, making it a natural fit for boats like the Mainship 30, Albin 28 Tournament Express, Back Cove, and countless similar Downeast and express cruisers. Whether found in an original installation or as part of a quality diesel repower, a well-maintained 6LPA continues to be a major selling point for buyers seeking dependable cruising power in the 28–32 foot range. For boaters who value mechanical simplicity, strong torque, and proven real-world longevity, the 6LPA series remains one of the standout engines of its class.