Outboard Engines From 50-75hp

Name: Outboard Engines From 50-75hp
Brand: JOHNSON

Outboards in the 50-75hp range are close to the limit before fuel consumption becomes a real issue. They suit planing hulls from 4.5-5.5m - those capable of being towed by four-cylinder cars

Outboards in the 50-75hp range are close to the limit before fuel consumption becomes a real issue.

They suit planing hulls from 4.5-5.5m - those capable of being towed by four-cylinder cars.

There is an extensive choice of engines in this range, with more and more four-strokes being added to the list. So much so, that some Trailer Boat readers face a dilemma - whether to choose a two or four-stroke.

Provided they're fitted to the right type of hull, I have a preference for four-strokes in this power range. But that doesn't mean they suit all applications.

For example, because of their higher compression ratios and greater mechanical complication, carburetted four-strokes won't troll as slowly as comparable two-strokes.
So if you're a freshwater fisho and don't want the fish-spooking problems of a trolling anchor under your boat, you either fit a carbie two-stroke and an electric trolling engine, or a fuel-injected four-stroke (the latter also has the advantage of being able to automatically adjust its air/fuel ratio according to barometric pressure and won't run rich on high altitude dams such as Eucumbene).

Remember, too, that servicing costs for four-strokes are higher than comparable two-strokes.

However, if you use your boat only for summer holidays and the odd long weekend, a two-stroke is the way to go.

In my opinion four-strokes don't suffer extended periods of disuse well and require oil and filter changes every six months (regardless of how few running hours are clocked up).
In comparison, providing it's been correctly 'winterised', a two-stroke outboard can be stored for up to a couple of years at a time without suffering any real internal damage.
Finally, the choice of hull is critical for good four-stroke performance.
Full-width transom pods such as the Maxi Transoms fitted to larger Quinnies are considered by many the way to go.

Please note: All prices quoted are current recommended retail only.

Two-Strokes

Johnson

There are three Johnsons available in this power range. All have a carburettor-per-cylinder, the same deep-ratio 2.42:1 gearcase and operate on a fixed 60:1 petrol/oil ratio via their OMS (Oil Management System) oil-injection.

At Wide Open Throttle (WOT), this ratio suits two-strokes better than any other.
All engines come standard with the four-channel 'System Check' visual and audible alarm system, which includes engine overheat and low oil flow/pressure sensing.

The twin-cylinder 50 started life in 1971 and though it has been upgraded over the years to improve idle quality, et al, is still the same classic engine as when first released.
It's one of the few big displacement (737cc) twins that won't shake your teeth out below 2000rpm and with power trim and tilt weighs a reasonable 86kg.

The electric-start, remote control version with PT&T retails for $7540.

The 60 and 70 are basically the same motor, have three-cylinders and displace 920cc.
They were released in 1985 and are bored-out versions of the 70 that dates back to the early 1970s.

Of course, 'Fastrak' PT&T and other improvements have been added, but these engines are still classics amongst mid-range two-strokes.

The power trim and tilt longshaft versions weigh 113kg and retail for $9260 and $9680 respectively.

Fitted to an Ally Craft 495 Centre Cabin, spinning a 17-inch pitch alloy prop and pushing a two-adult load, the test 70 averaged 41kmh on 4000rpm consuming 12lt/hr. The WOT average was 53kmh on 5400rpm consuming 29lt/hr. But over a mix of Dead Slow Troll (DST) operation and normal cruising, it consumed a mere 5lt/hr!

Mercury Marine (Mariner/Mercury)
Mariner and Mercury models in this power range comprise a three-cylinder, three-carbie 50, 60 and 75, plus a three-cylinder 65hp jet drive motor. All have oil-injection that varies from 50:1 at WOT to 100:1 at DST and mixes with the petrol at the fuel pump.

The 50 and 60 share the same 967cc powerhead, the biggest displacement of any engine in their horsepower classes.

In standard gear-ratio form (1.83:1) with power trim and tilt they weigh 93kg, but the Bigfoot 60 with 2.3:1 ratio weighs 108kg and is well-suited to pushing heavier planing hulls and semi-displacement workboats. The standard-ratio 50 and 60 retail for $8212 and $9190 respectively, while the 60 Bigfoot retails for $9550.

Mounted on a Quintrex Freedom Sport 488 Bowrider, spinning a 13-inch alloy prop and pushing a four-adult load, the test 50 cruised quietly at 26kmh on 4200rpm consuming 10lt/hr and wound out to 45kmh on 5500rpm using 23lt/hr.

The 75 is a de-rated version of the 90 described in Trailer Boat's 90-130hp Outboard Guide (Jan 2000) and displaces 1386cc.

In standard longshaft PT&T form it weighs 139kg, has a 2.3:1 gear ratio and retails for $10,243.

The 65 Jet has the same powerhead but the gearcase is replaced with a shrouded impeller that draws water up from under the motor, changes it to horizontal thrust and ejects through a steerable nozzle.

The unit operates in as little as 20cm of water. It weighs 143kg and retails for $12,650.

Tohatsu
In this power range are the three-cylinder, three-carbie 50, 60 and 70. All have oil-injection which varies from 50:1 at WOT to 100:1 at DST. The 50 displaces 697cc and in remote control PT&T longshaft form weighs 73kg.
It retails for $7723.

Lakeside Marine, the Aussie distributor for Tohatsu, intends releasing a Direct Fuel Injection version of this engine.

Known as the TDI50, it utilises the Orbital injection system which, with its air compressor functions, is not unlike the Mercury Optimax motors.

According to Orbital, this engine consumes 18lt/hr at WOT down to a mere 0.5lt/hr at DST.
The 60 and 70 share the same 938cc powerhead and 1.92:1 gear ratio.

In standard PT&T longshaft form they weigh 110kg and retail for $8584 and $9315 respectively.

Yamaha
Yamaha has the widest range of models in this category.

All, apart from the CV60 and CV75, have multipoint oil-injection which varies from 50:1 way down to 200:1 and injects oil at the reed valves.

All models have three-cylinders and three-carbies.

The 50 displaces 698cc, has a 1.85:1 gear ratio and weighs 87kg in longshaft PT&T form.
It retails for $8523.

The 60 and 70 share the same 849cc powerhead, 2.33:1 gear ratio and weigh 106kg in longshaft PT&T form. They retail for $9334 and $9613 respectively.

If you don't do much DST operation and you use your engine infrequently, consider the 50:1 premix CV60. It has the same performance as its oil-injected counterpart, but weighs 5kg less and is $1180 cheaper.

Mounted on a Southwind UB520, pushing a two-person load and spinning a 17-inch prop, the test 60 averaged 40kmh at 4000rpm consuming 10lt/hr. At WOT, the average was 56kmh on 5700rpm using 24lt/hr.

Apart from a few changes here and there, the CV75 is basically the same engine it was in late 1982 when first released on the Aussie market. Its 1140cc powerhead is a de-rated version of the 90 described in the 90-130hp Outboard Guide, but it uses a simple 50:1 premix. It has a 2:1 gear ratio and in standard longshaft PT&T form weighs a very reasonable 119kg.

It retails for $8170.

Pick Of The Bunch
Of the 50s, I believe the Mariner/Mercury 50 is the way to go. It's understressed and beautifully smooth for a three-cylinder engine. Of the 60s, I recommend the Yamaha 60 and especially its CV counterpart if you want real value for money.

And of the 70s, choose either the Johnson or Yamaha — the former for simplicity; the latter for cleaner running. Both are well-engineered and should stand up to years of hard work.

Four-Strokes

Evinrude

Two EFI models are offered in this range - the 50 and 70 - both of which are manufactured by Suzuki.

The three-cylinder crossflow 50 has chain-driven double overhead camshaft, a four-valve head and displaces 815cc. It has a 2.27:1 gear ratio and in standard longshaft PT&T form weighs 108kg. It retails for $9500. Mounted on a Stacer 459 Runabout, spinning a 14-inch alloy prop and pushing a three-adult load, the test motor averaged 26kmh on 4000rpm consuming 6-7lt/hr. The WOT average was 47kmh on 5800rpm and consumption around 16lt/hr.

The four-cylinder crossflow 70 has a single belt-driven camshaft and is based on Suzuki's Sierra 4WD motor. It displaces 1298cc, has a 2.42:1 gear ratio and in standard longshaft PT&T form weighs 149kg. It retails for $10,820. On an Ally Craft 495 Centre Cabin, spinning a 17-inch alloy prop and pushing a two-adult load, the test 70 averaged 35kmh on 4000rpm using 9lt/hr. The WOT average was 60kmh on 6200rpm using 20lt/hr.

Honda

In this power range, Honda offers two multi-cylinder engines — the BF50 and BF75. Both have a carbie-per-cylinder and belt-driven overhead cams, with the BF75 boasting a three-valve head.

The three-cylinder crossflow BF50 displaces 808cc and has a 2.09:1 gear ratio. In longshaft PT&T form it weighs 96kg and retails for $8390.

The four-cylinder crossflow BF75 is based on the venerable Civic car engine and is a de-rated version of the BF90 described in the 90-130hp Outboard Guide. It displaces 1590cc and has a 2.3:1 gear ratio. In longshaft PT&T form it weighs 169kg and retails for $11,550. Mounted on a 5.8m Stinger 619-E Fisherman, spinning a 17-inch alloy prop and pushing a two-adult load, at 4000rpm it averaged 39.4kmh consuming 7.5lt/hr. The WOT average was 58.8kmh on 5800rpm using 23lt/hr.

Trailer Boat's stablemate BlueWater has had considerable experience with the 75's 'big brother' 90hp unit and can vouch for its appeal.

Super quiet, smooth, economical and reliable, the only downside to the BF75/90 series is its considerable weight.

Mariner/Mercury
Two models are offered in this power range — a 50 and 75. Both have four-cylinder, four-carbie crossflow powerheads and belt-driven camshafts, but the 75 has twin cams and a four-valve head.

The F50 displaces 935cc and is available in standard and Bigfoot gearcase ratio models, both with standard PT&T. The longshaft standard model has a 2:1 ratio, weighs 102kg and retails for $7788, while the Bigfoot model's ratio is 2.3:1 and weighs 112kg. It retails for $8425.

The F75 is a de-rated version of the F90 described in the 90-130hp Outboard Guide and displaces 1596cc. It shares componentry with Yamaha's F110 powerplant, considered by many to be the pick of the big four-strokes. It has a 2.3:1 gear ratio, in standard longshaft PT&T form weighs 162kg and retails for $10,511.

Yamaha

One model is offered in this power range, though it comes with a choice of gear ratios.
Both motors have four-cylinder crossflow 935cc powerheads with belt-driven SOHC valve actuation.

The F50A is designed for aluminium hulls to 5m and has the same 1.85:1 gear ratio as its two-stroke counterpart. It weighs 102kg in standard longshaft PT&T form and retails for $9776.

With its 2.33:1 gear ratio, the F50B suits planing hulls and workboats to 6m and has proven popular with pro fishos in Queensland and the NT. It weighs 112kg and retails for $10,530.

Mounted on a Southwind UB580, spinning a 13-inch alloy prop and pushing a two-adult load, the test F50B planed us cleanly at 39kmh on 4400rpm and wound out to 48kmh on 5700rpm consuming 18lt/hr.

Pick Of The Bunch

Of the 50s, my choice is the Evinrude which not only outperforms its three-cylinder competition, but with its EFI escapes the potential carbie balancing problems.
But if you have to push a load and want slightly smoother-running, then consider the Yamaha F50B.

Amongst the 70s, the Evinrude is my all-round choice.

Again, its EFI eliminates carbie balancing problems and with its excellent mid-range torque (comparable to a two-stroke Yamaha 90) and deep gear ratio, it outperforms its heavier Honda BF75 competition.

But if you want an understressed work motor that's easier to repair in remote areas and returns better mid-range fuel economy than the Evinrude, then Honda's BF75 is the way to go.

Outboard Engines From 50-75hp

Tags