The Yanmar 6LY2A series is a 5.81-litre, six-cylinder inline marine diesel with mechanical direct injection, offered in two ratings: the turbocharged 6LY2A-UTP at 370 mhp and the turbocharged, intercooled 6LY2A-STP at 440 mhp, both rated at 3300 rpm. Part of Yanmar's long-running 6LY family, the 6LY2A built its reputation on power-to-weight — around 535 kg dry (without gear) for up to 440 mhp — in a compact package that drops neatly into twin shaft-drive engine rooms.
Its character is defined by the mechanical fuel system. With a conventional injection pump rather than common-rail electronics, the 6LY2A is straightforward to diagnose and service, which is a large part of why it remains popular with owners who put in serious hours on flybridge cruisers, game boats and other hard-working planing hulls.
The 6LY2A Series range
Both 6LY2A models share the same 5.81-litre block, footprint and weight, so the choice is about rating and duty cycle rather than fit. The 6LY2A-UTP delivers 370 mhp from a turbocharged engine without an intercooler — the more conservatively stressed rating, well suited to heavier hulls and owners planning big annual hours. The 6LY2A-STP adds an intercooler to reach 440 mhp, and makes sense on lighter planing hulls where top-end speed is the priority. In practice, hull weight, target cruise speed and gear ratio decide it: we assess your vessel and running gear, then confirm the match with propping data on sea trial.
Drive options
Shaft drive — Kanzaki KMH61A
The factory pairing on Yanmar's datasheet: a hydraulic Kanzaki 8-degree down-angle gear (the related KMH60A also appears on Yanmar's datasheets) with 1.55, 2.04 and 2.43 reduction ratios, suiting most planing and semi-planing shaft installations.
ZF 80A down-angle gear
Listed in Yanmar's 6LY2A literature as the HSW800A2, the ZF 80A is an 8-degree down-angle gearbox with 1.567, 1.750, 1.962 and 2.500 ratios — handy when a repower needs a different ratio spread or carries over existing ZF hardware.
Twin Disc MG5050A
A down-angle Twin Disc option listed in Yanmar's 6LY2A manuals, with ratios spanning roughly 1.12 to 2.50 — useful fine control when matching an existing shaft line and propeller during a changeover.
Other gear configurations
Yanmar's datasheet notes other gearboxes and configurations are available on request; for repowers we match the gear ratio to your running gear and verify propping on sea trial.
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 6LY2A Series from Mariner
Proven 6LY power-to-weight
Up to 440 mhp from a 5.81-litre inline-six at around 535 kg dry without gear. The 6LY2A earned its place in planing cruisers and game boats by packing genuine performance into a compact, shaft-drive-friendly footprint.
Mechanical simplicity
Mechanical direct injection with a conventional injection pump means straightforward servicing and diagnostics without complex engine electronics — a quality many high-hour owners still value.
Authorised Yanmar dealer support
Mariner Engineering supplies, installs and services Yanmar engines from Spotswood, with factory-trained technicians, genuine Yanmar parts, and repowers commissioned with a proper sea trial on Port Phillip Bay.
Yanmar 6LY2A Series — your questions answered
Should I choose the 6LY2A-UTP (370 mhp) or the 6LY2A-STP (440 mhp)?
They share the same 5.81-litre inline-six block, so size and weight won't decide it. The UTP is the lower-stressed, non-intercooled rating — the sensible pick for heavier hulls and big annual engine hours. The intercooled STP delivers the full 440 mhp and suits lighter planing hulls chasing speed. Duty cycle, hull weight and gearing settle the question, and we can run through that with you against your boat's numbers.
Will a 6LY2A work as a repower for my boat?
Often, yes — it's a compact inline-six that has replaced older 6LY-family engines and similar-capacity diesels in many shaft-drive cruisers and game boats. The down-angle gear options (Kanzaki KMH61A, ZF 80A, Twin Disc MG5050A) cover a wide ratio spread, which helps match an existing shaft line and propeller. We survey engine beds, shaft angle, cooling and exhaust before quoting, and every repower is commissioned with a sea trial on Port Phillip Bay.
Why choose the mechanical 6LY2A over Yanmar's common-rail 6LY400/6LY440?
The 6LY2A's appeal is its mechanical injection: no common-rail electronics, simple diagnostics and easy field servicing. The current common-rail 6LY400 and 6LY440 counter with quieter, cleaner running and current-generation emissions compliance. As an older-generation model, new 6LY2A availability varies, so we'll confirm what can be supplied and give you an honest steer on whether the 6LY-CR series is the better long-term fit.
Can you service a 6LY2A and supply genuine parts in Melbourne?
Yes. As an authorised Yanmar dealer we service the 6LY2A with factory-trained technicians and genuine Yanmar parts, from our Spotswood workshop or dockside around Port Phillip Bay. That covers routine servicing, injection pump and turbo work, heat exchanger and cooling system overhauls, and pre-purchase inspections on boats already fitted with these engines.
Ask about the 6LY2A Series 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 6LY2A Series model and drive, with pricing, usually within 1 business day.