Review: Yamaha F70A outboard motor

By: Andrew Norton

Presented by
  • Trade-A-Boat

Five years on and the Yamaha F70A outboard motor still has no directly competing marine engine.

Review: Yamaha F70A outboard motor
Best fuel efficiency on the Yamaha F70A outboard motor was delivered at 5000rpm.

What makes the Yamaha F70A outboard motor unique is that it weighs less than its Yamaha FT60D counterpart, yet has significantly more top-end torque and power. It’s the only four-stroke outboard in its power range that can be considered a repower alternative for older fibreglass runabouts (such as the Haines Hunter 445R) fitted with a two-stroke Johnson 70 or Yamaha 70B. The 75hp four-strokes are simply too heavy.

My local Yamaha dealers have told me that since its release in 2010 the F70A engine has been very popular with repowers of older boats, so Yamaha sure has scored here!

 

Yamaha F70A

At first glance the Yamaha F70A outboard could be mistaken for being an uprated version of the FT60D. It has the same base engine and gear ratio but that’s where the similarity ends. Instead of two valves per cylinder there are four, though still operated by a single belt-driven overhead camshaft and compact rocker arms. Because at 18.7mm the exhaust valve diameter is less than that in the FT60D the two valves only need one rocker arm to actuate them. At 24.5mm the intake valve diameter is much greater so one rocker arm per valve is needed. Three rocker arms operating four valves. Very clever!

To cope with higher electrical needs over the Yamaha FT60D a 17amp voltage regulated alternator is fitted, still a bit light in my opinion. But another clever touch is that if the engine management system picks up a sensor failure other sensors can compensate until a laptop computer is connected and the fault diagnosed. Yamaha’s Y-COP (Yamaha Customer Outboard Protection) offers remote keypad starting but make sure it’s attached to a small float!

The EFI system is tuned to run on standard 91 RON unleaded and as there’s no oxygen sensor in the exhaust passages, opting for premium 95 RON won’t give any performance benefits (although I’d use it anyway as it’s a better quality fuel and less likely to have some ethanol in it). At least if stale fuel of less than 91 RON is detected the ignition timing will retard to compensate. The trolling rpm can be altered in increments of 50.

 

Maintenance

As with the Yamaha FT60D powerhead access is very good and the engine oil dipstick and canister oil filter are easily reached. Yamaha FCW (Four Cycle Watercooled) SAE 10W30 engine oil is recommended and the 2lt sump provides adequate absorption of oil dilution that occurs during extended trolling periods. Valve clearance adjustments are done with a feeler gauge and spanner. The recommended servicing intervals are every 100 hours or annually after the first 20 hours and the camshaft timing belt should be replaced every
1000 hours. The warranty coverage is four years.

 

On the water

Damn! Neither review Yamaha engine gave my flab a workout but at least my tinnitus was given a break. Both engines started instantly hot or cold without a whiff of oil smoke and warmed quickly from cold. The Yamaha remote control boxes had precise shifting without any clunks, and providing the antiventilation plates were kept at least three-quarters immersed power astern was good, useful for backing off shoals. But because maximum torque appears to be developed around 4500rpm (the rpm limiter activates at 6500) the F70A outboard motor needs careful propping to deliver its full potential.

Mounted on a relatively light aluminium side console the first engine I tested had pretty good holeshot, though on a fibreglass cuddy cabin the second engine was a bit sluggish out of the hole. But it was pushing a total of 1100kg, a fair load for any 70, so this was to be expected.

Both engines refused to ventilate through tight turns at 4000rpm despite running alloy props and even at wide open throttle were quiet. Pity I didn’t have my decibel meter but I estimate WOT noise levels were below 90dBA.

 

The Trade-A-Boat verdict

The F70A outboard engine is compact, lightweight, easily maintained and serviced, and like all current Yammies has a proven reputation for survival in a marine environment.

The review engines were supplied by Yamaha Motor Australia, Murrarie-QLD, phone (07) 3906 7000. Or for more details and dealer locations, google Yamaha Motor Australia.

 

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Yamaha F70A sea trials

Yamaha F70A + Sea Jay 485 Haven Sports

Sea Jay 485 Haven Sports side console with single Yamaha F70A and 15in pitch alloy prop, total 950kg with three adults aboard. Average of two-way runs over low chop

RPM

SPEED (KTS)

FUEL BURN (LT/H)

700 (slow troll)

2.2

0.7

3200 (min plane)

11.6

7.3

3500 (min cruise)

16.4

9.2

4000 (cruise)

18.3

10.3

5000 (max cruise)

24.8

15.9

6000 (WOT)

30.2

22.1

 

Yamaha F70A + Cruise Craft 485 Explorer

Cruise Craft 485 Explorer with single Yamaha F70A outboard and 14in alloy prop, total 1100kg with three adults aboard. Average of two-way runs over low chop.

RPM

SPEED (KTS)

FUEL BURN (LT/H)

700 (slow troll)

2

0.7

2000 (fast troll)

5.9

3.4

3800 (min plane)

12.9

10.7

4000 (min cruise)

14.3

11.3

5000 (max cruise)

21.8

14.8

6400 (WOT)

29.9

23.4

* Note on this hull the best fuel efficiency was at 5000rpm. The speeds would be way higher and fuel flow less on a Haines Hunter 445, for example, totalling around 800kg with two adults aboard. Sea-trial data supplied by the author.

 

Related: Steve Starlo's five-year evaluation of a Yamaha F70A

 

Yamaha F70A specs

PRICE $10,400 long shaft RRP

TYPE Four-cylinder four-stroke 16-valve EFI outboard motor

RATED BHP/MHP* 69/70 at 5800

REC. RPM RANGE 5300 to 6300

DISPLACEMENT 996cc

BORE X STROKE 65 x 75mm

GEAR RATIO 2.33:1

WEIGHT 119kg (dry, long shaft); 121kg (dry, extra-long shaft)

OEDA stars 3

* Brake horsepower/Metric horsepower or PS

 

See the full version of this review in Trade-A-Boat #467, July / August 2015. Why not subscribe today?

 


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