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Bertram 31 (1981) - Yanmar Repower (Not Prod)
(w/ 2 x 315-hp Yanmar 6LPA-STP2 Diesel)

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Innovations and Differences in the Motor Mounts

Capt. Robert Smith of BoatTEST takes us on a tour of the steel motor mounts in Bertram's engine room.
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Brief Summary

Just sprucing up the interior, updating the electronics and maybe adding a new paint job isn’t enough when you are trying to take a classic like the 31 Bertram and breathe new life into her. Richard Mastry of Mastry Engine Center in St. Petersburg, Florida recently took us on a ride down memory lane with one of his passions-- repowering beautiful old Bertrams. He has repowered over 30 of them, so we would call him a pro and since he helped bring Yanmar marine engines into the US, he could also be considered a professional resource for repowering a boat with Yanmar engines. This particular model has been repowered with twin Yanmar 6LPA-STP2s.

Key Features

Key Features of 6LPA-STP2:
  • Compact profile
  • Easy access to maintenance points
  • 24 valve overhead cam 6 cylinder in-line four stroke 4.1 liter
  • 899 lbs per engine
  • Gear reduction starter
  • Two-stage fuel injectors
  • 80 amp alternator
  • Cast stainless mixing elbow for longer life
  • Wet turbo
  • Multiple transmissions available

    **Contact Bertram Yachts for complete model information**
  • Specifications

    Length Overall 30' 7''
    Beam 11' 2''
    Dry Weight 9, 400 lbs. (with fuel)
    Tested Weight N/A
    Draft 2' 7''
    - Draft Up N/A
    - Draft Down N/A
    - Air Draft N/A
    Deadrise/Transom N/A
    Max Headroom 6' 2''
    Bridge Clearance 8' 0''
    Weight Capacity N/A
    Person Capacity N/A
    Fuel Capacity 220 gal.
    Water Capacity 18 gal.
    Length on Trailer N/A
    Height on Trailer N/A
    Trailer Weight N/A
    Total Weight
    (Trailer, Boat, & Engine)
    N/A

    Prices, features, designs, and equipment are subject to change. Please see your local dealer or visit the builder's website for the latest information available on this boat model.

    Engine Options

    Std. Power Not Available
    Tested Power 2 x 315-hp Yanmar 6LPA-STP2 Diesel
    Opt. Power 2 x 315-hp Yanmar 6LPA-STP2

    Test Results - Change Measurement Unit

    RPM MPH Knots GPH MPG NMPG Stat. Mile NM dBa
    1250 8.5 7.3 2.7 3.1 272.0 620 539 83
    1500 9.2 8.0 4.3 2.1 1.9 421 366 84
    1750 10.1 8.8 6.2 1.6 1.4 323 280 85
    2000 15.9 13.8 7.9 2.0 1.7 397 345 85
    2250 20.1 17.4 10.0 2.0 1.7 397 345 86
    2500 23.7 20.6 12.4 1.9 1.7 378 329 87
    2750 26.4 23.0 14.4 1.8 1.6 363 316 88
    3000 29.5 25.6 16.7 1.8 1.5 349 304 90
    3250 31.3 27.2 19.1 1.6 1.4 324 282 89
    3500 34.0 29.6 23.3 1.5 1.3 289 251 90
    3750 35.9 31.2 26.8 1.3 1.2 265 231 90
    3911 37.4 32.5 29.4 1.3 1.1 252 219 91
    RPMNMKMKPHLPHKPLdBA
    1250 539 998 13.70 10.22 1.33 83
    1500 366 678 14.80 16.28 0.91 84
    1750 280 520 16.30 23.47 0.69 85
    2000 345 639 25.60 29.90 0.85 85
    2250 345 639 32.30 37.85 0.85 86
    2500 329 608 38.10 46.94 0.81 87
    2750 316 584 42.50 54.51 0.78 88
    3000 304 562 47.50 63.22 0.75 90
    3250 282 521 50.40 72.30 0.70 89
    3500 251 465 54.70 88.20 0.62 90
    3750 231 426 57.80 101.45 0.57 90
    3911 219 406 60.20 111.29 0.54 91

    All fuel consumption numbers are the total for all engines in the boat. Speeds are measured with Stalker ProSports radar gun or GPS. Fuel consumption (gallons per hour) measured with Floscan digital fuel-flow meter or by on-board factory-installed diagnostic instruments. Range is based on 90% of published fuel capacity. Sound levels determined using Radio Shack digital decibel meter on A scale. 68 dBA is the level of normal conversation. Time to plane is measured from start of acceleration to formation of rooster tail behind boat.

    Performance Chart

    Performance Chart

    Acceleration Times & Test Conditions

    Time To Plane 5.3 sec.
    0 to 30 8.4 sec.
    Ratio 2:1
    Props Michigan 18 x 25 4 blade broze
    Load 3 pers., Fuel 107 gal., Water 12 gal , min. gear
    Climate Temp: 90 deg., humid: 47%, wind: 5 mph, 10 mph: min chop

    Test Result Highlights

    • Top speed for the Bertram 31 (1981) - Yanmar Repower (Not Prod) is 37.4 mph (60.2 kph), burning 29.4 gallons per hour (gph) or 111.28 liters per hour (lph).
    • Best cruise for the Bertram 31 (1981) - Yanmar Repower (Not Prod) is 20.1 mph (32.3 kph), and the boat gets 2.01 miles per gallon (mpg) or 0.85 kilometers per liter (kpl), giving the boat a cruising range of 397 miles (638.91 kilometers).
    • Tested power is 2 x 315-hp Yanmar 6LPA-STP2 Diesel.

    Standard and Optional Features

    Warranty

    Full Warranty Information on this brand coming soon!

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