FOR THOSE WHO UNDERSTAND WHAT TRUE PERFORMANCE IS MADE OF
YOU'VE OWNED
FAST BOATS.
THIS IS DIFFERENT.
The Koshi 51 weighs 4,200 kg fully rigged. A 17.5-metre hull lighter than most 10-metre boats. Full carbon fiber, everywhere it matters — and +100 mph to prove it.
Full Build Weight
4,200 kg
17.5 metres. Lighter than most 10m fibreglass hulls. That’s what full carbon fiber actually means.
Verified Top Speed
+100 mph
See it in action
Built By
Koshi Marine
100% CF
Koshi Group has manufactured carbon fiber components since 2009 — including for motorsport. The 51 is what happens when that crosses into marine.
Technical Specifications
Specs
Every number you need to make a decision. If you want the full engineering file — hull scantlings, engine options, systems layout — request the technical pack.
As seen on The Boat Show
Maurizio Bulleri
Hear from someone who has spent a career testing the world’s most high-performance boats…
See what he has to say about KOSHI 51
As seen on The Boat Show
Maurizio Bulleri
Hear from someone who has spent a career testing the world’s most high-performance boats.
See what he has to say about KOSHI 51…
The Experience
Reading About
It Does Nothing.
It Does Nothing.
The only thing that converts a spec sheet into a purchase decision is opening the throttle in person. Arrange that.
COMING SOONBorn to lead and be the First. No matter the conditions.
Saturday, 23 May 2026
The questions every serious buyer asks
Honest
Answers.
Answers.
Is 100+ mph actually real, or is that a marketing number?
It's real. GPS-logged, independently witnessed, standard production build. No stripped interior, no race props, no asterisk. We'll prove it on your sea trial — and you'll be the one looking at the GPS screen, not us.
Is it really full carbon fiber, or just carbon trim on a glass hull?
Full carbon fiber monocoque. Hull, deck, structural members — all carbon, all in-house. Koshi Group has been building carbon fiber structural components since 2009, including for motorsport. This isn't a first attempt at carbon marine. It's the application of 15 years of engineering to a boat.
What does a boat like this actually cost to run?
Less than you'd expect. The carbon hull requires no antifoul cycle, no osmosis treatment, and no gelcoat maintenance. Engine servicing follows standard Mercury intervals. We'll put you in touch with two current owners to ask them directly — no filters, no scripts.
Can I specify the boat differently, or is it fixed?
Engine configuration, interior layout, electronics package, and colours are all customisable. The hull, carbon structure, and performance envelope are fixed — because that's what makes the 51 what it is. We'll walk you through options on the demo.