1978 Bertram 31 Boat in Winthrop Harbor, IL US
Built in 1978
31
2 Engines (2x MERCRUISER)
31 feet
Gas
Fiberglass/Reinforced
Price History
| Date | Event | Price |
|---|---|---|
| 5/20/26 | Initial price | $119,900 |
1978 Bertram 31 Video Tours
Boattest.com Review
Overview
This review examines the impact of repowering a 1981 Bertram yacht with modern Yanmar 6LP series diesel engines. Originally equipped with two 330 horsepower Mercruiser 454 gasoline engines, the vessel underwent an upgrade to twin Yanmar 6LPA STP II diesel engines. This transition not only improved efficiency and operational security but also added value by reducing weight and fuel consumption while freeing up valuable engine room space.
Engine Design and Installation
The Yanmar 6LPA STP diesel engine features a compact design that fits easily within the existing engine stringers of the Bertram, creating an additional 3 inches of space on the inboard side and sufficient room on the outboard side to accommodate a small generator. The aft end of the engine also gained 5 inches of clearance. Despite its compact profile, the engine maintains accessibility to key maintenance points, including oil dipsticks on both sides, a spin-on oil filter, a secondary fuel water separator filter, and a primer pump located on the inboard side. The heat exchanger is positioned high on top with hoses routed around the front, while the stainless steel mixing elbow, wet turbocharger, compressor, and air intake are arranged efficiently at the aft end. The transmission cooler and hoses are located below these components. This layout significantly improves space utilization compared to the original large-block gasoline engines, allowing easier access to batteries and additional equipment placement.
Engine Specifications and Performance
The 6LPA STP is a 6-cylinder, 4-stroke, 4.1-liter turbocharged diesel engine equipped with an intercooler and a fresh water cooling system, which is considered optimal for marine applications. It delivers a continuous rating of 255 horsepower at 3600 RPM and a maximum output of 315 horsepower at 3800 RPM, weighing 899 pounds. The repowered Bertram achieved planing in 5.3 seconds and reached 30 mph in 8.4 seconds. At maximum RPM (3911), the engines consumed 29.4 gallons per hour, providing a range of 254 miles at 37.4 mph. Operating closer to the continuous rating at 3500 RPM, fuel consumption dropped to 23.3 gallons per hour, extending the range to 292 miles at 34 mph. The most economical cruise speed was 20.1 mph at 2250 RPM, yielding a range of 401 miles. These figures highlight the improved fuel efficiency and extended cruising capabilities afforded by the diesel repower.
Operational Benefits and Owner Experience
The repower delivered significant benefits including reduced engine weight, increased available space, and easier maintenance access, all contributing to safer and more economical operation. The owner noted that the only unexpected cost was repainting the waterline due to an overall weight reduction of approximately 3,000 pounds from the new engine installation. The diesel engines provide peace of mind through reliable and efficient performance, promising many years of enjoyable boating. The reviewer also emphasizes the advanced engineering of Yanmar's latest diesel models and recommends considering Yanmar power for both repowers and new yacht specifications.
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Boats For Sale in Illinois, United States Similar to the 1978 Bertram 31
Compare with similar boats and find the perfect one for you.
 1978 Bertram 31 | |||||
|---|---|---|---|---|---|
| $119,900 | $119,900 | $89,999 | $72,999 | $69,995 | $62,000 |
| Winthrop Harbor | Winthrop Harbor | Waukegan | Mchenry | Round Lake | Grafton |
| 31' | 31' | 32' | 25' | 23' | 47' |
| MERCRUISER | MERCRUISER | Volvo | - | Yamaha | Crusader |
| 310 hp | 310 hp | 375 hp | - | 200 hp | - |
| 26 | 40 | 562 | 42 | 51 | 18 |
Other 1978 Bertram 31 For Sale in Illinois, United States
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Contact SkipperBud's Northpoint about 1978 Bertram 31
Winthrop Harbor, IL
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