Review of Yamaha 25 Mk II
Basic specs.
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The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season. And outside the sailing season, just bottom cleaning and perhaps anti-fouling painting once a year - a few hours of work, that's all.
The Yamaha 25 Mk II is equipped with a masthead rig. The advantage of a masthead rig is its simplicity and the fact that a given sail area - compared with a fractional rig - can be carried lower and thus with less heeling moment.
Fin keel
The Yamaha 25 Mk II is equipped with a fin keel. A boat with a fin keel is more manoeuvrable but has less directional stability than a similar boat with a full keel.
The boat can enter most marinas as the draft is just about 1.65 - 1.75 meter (5.41 - 5.71 ft) dependent on the load. See immersion rate below.
The boat may be equipped with an inboard Yanmar diesel engine at 8 hp (5 kW). Calculated max speed is about 4.8 knots
Sailing characteristics
This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.
What is Capsize Screening Formula (CSF)?
The capsize screening value for Yamaha 25 Mk II is 2.31, indicating that this boat would not be accepted to participate in ocean races.
What is Theoretical Maximum Hull Speed?
The theoretical maximal speed of a displacement boat of this length is 5.9 knots. The term "Theoretical Maximum Hull Speed" is widely used even though a boat can sail faster. The term shall be interpreted as above the theoretical speed a great additional power is necessary for a small gain in speed.
The immersion rate is defined as the weight required to sink the boat a certain level.
The immersion rate for Yamaha 25 Mk II is about 107 kg/cm, alternatively 601 lbs/inch.
Meaning: if you load 107 kg cargo on the boat then it will sink 1 cm.
Alternatively, if you load 601 lbs cargo on the boat it will sink 1 inch.
Sailing statistics
This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.
What is Motion Comfort Ratio (MCR)?
The Motion Comfort Ratio for Yamaha 25 Mk II is 14.8.
What is L/B (Length Beam Ratio)?
The l/b ratio for Yamaha 25 Mk II is 2.77.
The ballast ratio for Yamaha 25 Mk II is 38%.
What is Displacement Length Ratio?
The DL-ratio for Yamaha 25 Mk II is 234 which categorizes this boat among 'light crusers & offshore racers'.
What is SA/D (Sail Area Displacement ratio)?
The SA/D for Yamaha 25 Mk II with ISO 8666 reference sail is 19.8, with a 135% genua the SA/D is 23.5.
Maintenance
When buying anti-fouling bottom paint, it's nice to know how much to buy.
The surface of the wet bottom is about 19m2 (204 ft2).
Based on this, your favourite maritime shop can tell you the quantity you need.
Note: If you use a paint roller you will need more paint than if you use a paintbrush.
Dimensions of sail for masthead rig.
Are your sails worn out? You might find your next sail here: Sails for Sale
If you need to renew parts of your running rig and is not quite sure of the dimensions, you may find the estimates computed below useful.
| Usage | Length | Diameter | ||
| Mainsail halyard | 24.1 m | (79.0 feet) | 8 mm | (5/16 inch) |
| Jib/genoa halyard | 24.1 m | (79.0 feet) | 8 mm | (5/16 inch) |
| Spinnaker halyard | 24.1 m | (79.0 feet) | 8 mm | (5/16 inch) |
| Jib sheet | 7.5 m | (24.8 feet) | 10 mm | (3/8 inch) |
| Genoa sheet | 7.5 m | (24.8 feet) | 10 mm | (3/8 inch) |
| Mainsheet | 18.9 m | (61.9 feet) | 10 mm | (3/8 inch) |
| Spinnaker sheet | 16.6 m | (54.5 feet) | 10 mm | (3/8 inch) |
| Cunningham | 2.8 m | (9.2 feet) | 8 mm | (5/16 inch) |
| Kickingstrap | 5.6 m | (18.4 feet) | 8 mm | (5/16 inch) |
| Clew-outhaul | 5.6 m | (18.4 feet) | 8 mm | (5/16 inch) |
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