The 6LT is the largest and most powerful family in Yanmar's common-rail marine range, unveiled alongside the 6LF series at boot Düsseldorf in 2020. It is a turbocharged, intercooled inline six-cylinder diesel with Bosch common-rail injection and full electronic engine management, offered in three ratings — 500, 580 and 640 mhp, all delivered at 2,530 rpm. The family took Yanmar's common-rail line-up well past its previous 440 mhp ceiling, into territory traditionally held by bigger, heavier engines.
Yanmar designed the 6LT for planing and semi-planing hulls, where power-to-weight matters — the bare engine is quoted at around 1,125 kg dry without gearbox, a compact package for the output on offer. Common-rail injection keeps combustion quiet, clean and efficient across the rev range, and the standard package includes Yanmar's VC20 vessel control system: CAN-bus electronic throttle and shift, a colour multifunction display and NMEA 2000 engine data output, on 24-volt electrics.
The 6LT-CR range
All three models share the same six-cylinder block, turbocharging and Bosch common-rail hardware — the difference is rated output, so the choice comes down to hull weight, target speed and how hard the engines will work. The 6LT500 suits heavier hulls and higher annual hours, where a conservatively rated engine cruises with margin in reserve; the 6LT580 is the middle path for cruisers wanting stronger mid-range performance; and the 6LT640 is the top rating for lighter planing hulls in recreational duty, where outright speed matters more than long daily running. Duty ratings and certification requirements can also differ between outputs and applications, so for charter or survey work the right answer isn't always the biggest number — tell us the boat and how you use it, and we'll size the engine and confirm performance at the commissioning sea trial.
Drive options
Shaft drive
The 6LT is a shaft-drive inboard, supplied as a complete Yanmar package with a ZF marine gearbox — typically from the ZF305 series — in a choice of reduction ratios to suit the hull and propeller.
Angled, parallel & V-drive gearboxes
Yanmar offers the 6LT with angled, parallel or V-drive gearbox configurations, letting the engine sit further aft where accommodation space or weight distribution demands it.
VC20 controls & joystick option
Every 6LT runs Yanmar's VC20 vessel control system — CAN-bus electronic throttle and shift with a colour multifunction display and NMEA 2000 output. Yanmar's JC20A inboard joystick is designed for twin shaft installations with a bow thruster on compatible engines; we can confirm whether it suits a given 6LT project.
Boats this family suits
Pricing, repower advice or a spec for your boat
Tell us your vessel and how you use it — we'll recommend the right model and drive, with dealer pricing.
Why buy your 6LT-CR from Mariner
Flagship common-rail performance
The 6LT crowns Yanmar's common-rail range at 640 mhp. Bosch common-rail injection and electronic engine management deliver strong, clean torque for planing hulls, with the low noise and smoke expected of a modern leisure diesel.
Compact and light for the power
A turbocharged, intercooled inline six quoted at roughly 1,125 kg dry without gearbox — a genuinely compact package for a 500–640 mhp diesel, which is exactly what a repower of older, heavier machinery needs.
Authorised dealer, full repower service
Mariner Engineering supplies new 6LT engines from Spotswood in Melbourne's west with the whole job behind them: installation engineering, gearbox and propeller matching, sea-trial commissioning on Port Phillip Bay, factory-trained servicing and genuine parts.
Yanmar 6LT-CR — your questions answered
Which model should I choose — 6LT500, 6LT580 or 6LT640?
They're the same physical engine at different ratings, so it's about matching output to your hull and usage. Heavier hulls and high annual hours favour the 6LT500's conservative rating; lighter planing hulls chasing top-end speed in recreational use suit the 6LT640. We size engines from your hull's weight, waterline and current performance rather than guesswork, and confirm the result with a sea trial on Port Phillip Bay.
Will a 6LT fit as a repower for my current engines?
Often, yes — the 6LT is compact and relatively light for a 500–640 mhp diesel, which helps when replacing older engines of similar output. But every repower hinges on engine beds, shaft angle, gearbox ratio, cooling and exhaust routing, so we start with an on-boat survey before quoting. And if the 6LT isn't the right fit, we're also dealers for Volvo Penta and the rest of the Yanmar range, so the advice isn't tied to one engine.
Is the 6LT available with a sterndrive or saildrive?
No — the 6LT-CR series is a shaft-drive inboard only, paired with ZF marine gearboxes in angled, parallel or V-drive configurations. Yanmar's sterndrive and saildrive options sit further down the range on the smaller engine families; at this power level, shaft drive is the standard approach.
Who services the 6LT in Melbourne, and what about warranty?
We do. As an authorised Yanmar dealer, Mariner Engineering handles warranty work, scheduled servicing and diagnostics for the 6LT and its VC20 control system, using factory-trained technicians and genuine Yanmar parts. We're based in Spotswood and look after vessels across Port Phillip Bay and Victoria — call (03) 9399 5888.
Ask about the 6LT-CR range
Tell us your vessel, how you use it, and whether this is a new build or a repower — our team will recommend the right Yanmar 6LT-CR model and drive, with pricing, usually within 1 business day.