Review of Bonum 25

Basic specs.

The Bonum 25 is a small motorboat designed by the Swedish maritime architect Per Brohäll in the early eighties. The Bonum 25 is built by the Swedish yard Bonum Marin.

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Hull

Both the hull and the deck 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 deck is a double deck which improves the indoor climate.

Interior

The interior is like most other boats made of teak. Teak has the advantage of being naturally very oily and therefore water-repellent, which is suitable on boats.
The boat is equipped with 4-5 berths and a galley.

Keel

The boat can enter even shallow marinas as the draft is just about 0.70 - 0.80 meter (2.30 - 2.60 ft) dependent on the load. See immersion rate below.

Engine

Bonum 25 is typically equipped with an inboard Volvo Penta MD17D diesel engine at 36.0 hp (26 kW).

The fuel tank which is made of stainless steel has a capacity of 110 liters (29 US gallons, 24 imperial gallons).

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.

Immersion rate

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Bonum 25 is about 132 kg/cm, alternatively 743 lbs/inch.
Meaning: if you load 132 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 743 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.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Bonum 25 is 2.93.

Compared with other similar motor boats it is slimmer than 58% of all other designs. It seems that the designer has chosen a slightly more speedy hull design.

Curiosities

Powerboat?

In Denmark, you are required to have achieved a 'powerboat driving license' in order to sail a powerboat.
In this context a boat is considered a powerboat if:

Danish definition of a powerboat

According to this definition this boat is not categorized as a Powerboat.
Though, if you install a motor of 61 kW (81 hp), then the boat will become a powerboat, and you will need a Danish 'powerboat driving license'

Maintenance

Boat owner's ideas

This section is reserved boat owner's changes, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.

Finally

We are always looking for new photos. If you can contribute with photos for Bonum 25 it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us. Criticism helps us to improve.

References

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