When it comes to motorising family day boats, RIBs and even bigger centre consoles the gap between 150hp and 200hp is a mighty wide one, so this brand new F175A from Yamaha is an important gap filler for them and helps to create a logical and incremental power line from 2.5hp all the way through to 350hp.
The Yamaha F175A will be on display at Southampton Boat Show on the Yamaha Stand: E072, and on the marina at the Jeanneau power stand: M439.
To slot neatly in the Yamaha family of outboards in this larger sector the same 2.8-litre block from the F200 has been used as the base, but this is not just a de-tuned 200hp motor. It is in fact, a new engine using a new head, new valve gear, new alternator and a new air inlet system. Even the cowling has been redesigned with a new shape and uses a different resin matrix that reduces the weight of the cowling considerably. Comparing the new lid to the old one it is amazing how much dead weight there was in the old cover. Thanks to the weight loss program that Yamaha have put their engines on, the new engine is a lithe 225kgs. This sleek, lightweight and compact motor is awash with new technologies.
The F175A uses the modern concept of an offset crankshaft to reduce frictional losses within the engine and to help make the whole engine more compact. By offsetting the crankshaft by 10mm from the centreline of the bore there is less lateral pressure on the cylinder wall during the power stroke which releases more of the power made for propulsion.
The head arrangement for the new F175A incorporates standard double overhead camshafts (DOHC), without the variable camshaft timing of the bigger motors, but retains the 4-valves per cylinder to ensure efficient transfer of the combustion gases. The VCT is unnecessary to produce 175hp from the 2.8 litres available and the motor runs perfectly happily using what might now be termed ‘old school’ simple engineering in a relatively unstressed format. After all, at just 63hp per litre the engine can hardly be described as being in a high state of tune. This will appeal to those commercial operators who want longevity from their engines and a pair of these new F175 motors will provide the same power as one of the mighty V8 F350s.
Another weight saving operation was the redesign of the centre section, combining the exhaust and oil pan in two castings that make life easier for the maintenance department and the combined weight is less than the original one piece mid-section. The mounting bracket has also had a surgical makeover, replacing the three hydraulic rams for the trim and tilt with one, large ram placed centrally where it is better protected. The mounting bracket and trunnion is necessarily wider to accommodate the hydraulics, but that has been redesigned with webs to make it stronger yet lighter and spreads the load over a wider section of the transom, which reduces the vibrations transferred though the hull as a added bonus.
This is all well and good, but the final piece of the jigsaw is the contact with the water. To continue the improvements down the drive train Yamaha have had a close look at the final drive arrangement and have come up with a new drive coupling that incorporates a robust cush drive which deforms progressively as the power is applied until there is direct contact for highest efficiency of power transfer. As the gears are engaged the cush drive softens the take up to provide a silken transition to the propeller.
On the water
So, what is it like out on the water, that is what everyone really wants to know. We had an opportunity to put that to the test on a typical, lightweight family centre console, the Jeanneau Cap Camarat 6.5 and an altogether heavier family day cruiser in the Finnmaster 68DC.
On the Jeanneau the F175 comes in under the upper limit of the boats 200hp rating. The new F175 offers a weight saving without drastically reducing the performance, but the lighter transom weights provides better balance for an enhanced driving experience. On the longer and heavier Finnmaster there is the capability for 250hp so the F175 is in the middle of the recommended power range and suits the lines without overwhelming the transom. Exactly what the Yamaha engineers were aiming for.
As is to be expected with the march of progress, the new engine is whisper quiet, despite not having any acoustic deadening on the interior of the cowling. I had to check the tell tale or tacho to know if it was running at idle because from a few feet away I couldn’t hear it. As we cast off and I slid the lever forward there was a tangible knock as the gears engaged, but no gnashing of teeth or heavy clunk, thanks to the cushioning provided by the rubber cords and without having to go to the lengths of fitting electronic control. The F175, whilst stoically cable controlled, is a smooth operator.
Making our way out of the marina at just above tick-over, so as to stay within the speed limit and restrict our wash, was virtually silent running, like an electric boat. Only when we cleared the harbour entrance and really opened her up did the sound of the intake become noticeable. The noise was like a hive of bees fanning the colony, just a rhythmic hum and the rushing sound of air being sucked in, to breathe life into the four-chambered heart of the matter. In realistic terms the sound of the engine played second fiddle to the noise of the water and air rushing by, so it becomes part of the audible atmosphere, rather than imposing over the top of the acoustic surrounds.
The power delivery is linear throughout the rev range with no flat spots, thanks to the electronic fuel injection and engine management keeping things at the optimum for the demand. The F175A is a logical addition to the Yamaha line up that provides a capital outlay advantage over the F200 without reducing the performance greatly.
Yamaha F175A: Engine specifications
Engine type Four stroke, 16-Valve, DOHC, In-Line 4
Displacement: 2785 cc
Bore x Stroke: 96.0 mm × 96.2 mm
Max. Propeller Shaft Output: 128.7 kW (175 ps) @5500 r/min
Full Throttle RPM Range: 5000 - 6000 r/min
Gear Ratio: 1.86 (26/14)
Dry Weight: (with prop)
L shaft: 224 kg
X shaft: 225 kg
Throttle and Shift Controls: Mechanical Control
Max. Alternator Output: 50 A
Price (incl VAT): Version L to fit 20in (508mm) transom heights: F175AETL £16,499
and Version X to fit 25in (635mm) transoms: F175AETX £16,999
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