Review of Yamaha 25 Mk II

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 boat 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.

The boat is typically equipped with an inboard Yanmar diesel engine at 8.0 hp (5 kW), which gives a max speed about 4.8 knots.

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.

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Yamaha 25 Mk II is 14.8.

Comparing this ratio with similar sailboats show that it is more comfortable than 31% of all similar sailboat designs. This comfort value is just below average.

What is L/B (Length Beam Ratio)?

The l/b ratio for Yamaha 25 Mk II is 2.77.

Compared with other similar sailboats it is more spacy than 76% of all other designs. It seems that the designer has chosen a significantly more spacy hull design.

What is Displacement Length Ratio?

The DL-ratio for Yamaha 25 Mk II is 234 which categorizes this boat among 'light crusers & offshore racers'.

46% of all similar sailboat designs are categorized as heavier. A heavy displacement combined with smaller water plane area has lower acceleration and is more comfortable.

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.

The SA/D ratio indicates that it is faster than 79% of all similar sailboat designs in light wind.

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.

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[Ref 1]: ISO 8666 Small craft — Principal data.
[Ref 3]: ISO 12215-5 Small craft — Hull construction and scantlings.