Akuna shows the way forward in boat repower with Yanmar 4LHA-STZP dual engine power source
by Power Equipment 28 Apr 2020 14:48 AEST
The “Akuna” was a good boat with potential for so much more. The recent repower with a pair of Yanmar 4LHA turbo-diesel engines has revealed the true potential of this yacht club stalwart © Power Equipment
Yanmar's popular 4LHA turbo-diesels have ensured a yacht club start/rescue boat can give the durable support expected while using a fraction of fuel compared to its original engine setup.
It is perhaps a sign of providence that the Townsville Yacht Club named its 7.9 metre Ozycat start/rescue boat Akuna, an Aboriginal word that translates to "flowing water" and "the way forward".
The boat was purchased in 2016, but a repower in 2019 with ever-reliable 4LHA-STZP Yanmar/Bravo sterndrive packages has helped deliver a dependable and fuel-efficient support vessel for the club into the future.
"We wanted a safe, comfortable platform primarily for running day races and other events," explained Townsville Yacht Club (TYC) member and commercial skipper Mick Malone.
"It is a boat that will usually be handled by the delegated club officer of the day during race events, but can also be used as a rescue or retrieval vessel to tow a stricken yacht home."
Power Equipment supplied the Townsville Yacht Club its 4LHA-STZP engine packages with the heavy duty Mercruiser Bravo 2X sterndrive incorporating a large diameter single three-blade aluminium propeller.
They replaced European-branded V8 petrol engines and legs that were not only costing a lot to run at the petrol bowser, but were proving unreliable and expensive to maintain.
The Yanmar repower into the TYC's support cat is yet another perfect example of just how versatile the 4LHA engine can be for both catamarans and monohulls. Its compact size and sterndrive, shaft and waterjet configurations have made it an option for literally hundreds of new and repower applications in both production and custom hulls in the Australian and New Zealand markets.
Mick Malone is an experienced commercial skipper, captaining port tug boats for many years and offering other skippering services. He was keen to recommend the Yanmar conversion for the Townsville Yacht Club's boat, given he runs similar engines in his own live-aboard catamaran.
The 240mhp @ 3,300rpm rated Yanmar 4LHA-STZP engines aren't just built to last - they are also relatively light weight and easy to service - another helpful advantage for a club boat.
A world-class power-to-weight ratio direct injection turbo diesel engine, (the engine itself weighs in at just under 390kg), contrary to traditional diesel running the 4LHA is also a low smoke and low vibration engine at both idle and acceleration.
With more than 80 hours clocked up on the Yanmars since their installation in Akuna, fuel consumption hasn't been the only advantage to the club.
Fuel consumption "more than halved" after Yanmar installation
"We have at least halved our fuel consumption easily with these engines," estimates Mick, "and of course we have the reliability and confidence of new engines which is nice."
With a displacement of 3.455 litres, the 4LHA uses a turbocharger with a waste gate boost compensator to improve acceleration performance.
Despite a reluctance among many to use a four-cylinder diesel due to high vibration levels being inherent with some brands, the Yanmar 4LHA series does not share such annoying traits. The lively performance of this engine has always impressed users with its smooth operation right across its rpm range and no-fuss simplicity.
Output from this four-cylinder diesel is evident in propeller power right through its power curve. However even at 3,000rpm (just a few hundred revs under its maximum-rated running revs) the 4LHA consumes less than 40 litres/hour of fuel.
With a continuous power rating of 190mhp @ 3,100rpm, the advantages of this Yanmar package become even more evident, particularly for the possible tasks of Akuna in its club duties.
"The boat can be used as a support vessel for overnight events out towards nearby islands (up to 45 nautical miles away) or beyond, so there will be times it will be required for longer hauls," explained Mick.
So while Akuna's 4LHA power curve can give speed if required, a torque peak in the mid-to-high 2,000rpms range delivers very efficient running (a little over the mid-20's litres/hour per engine) if a long range tow or event support run over longer distances is required.
In all, a winning combination that will no doubt serve the Townsville Yacht Club well - and serious food for thought amongst those looking for the smartest "way forward" in their own new or used boat power needs.