2010 Yamaha 70-hp, Portable 4-Strokes, and More

The Outboard Expert has the goods on the SDS propeller hub, lighter-weight portables, and a redesign aimed at the re-power market.

January 22nd 2010

The new 4.2-liter Offshore and V Max V-6 stole the show at the Yamaha media launch in November, but there is other news from that event that I just didn’t have room to report at the time. Let’s start with a left-over tidbit from the V-6 intro, the new SDS propeller hub.

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A re-tuned version of the Yamaha F60, the new 260-pound F70 will be the lightest motor in this class, and a good match for compact bass boats.

New prop hub design – no more shifting clunk

The Shift Dampener System (SDS) is a feature of Yamaha Saltwater Series II props, now offered in 13-inch to 23-inch pitch – the 13 and 23 are new to the line. The purpose of SDS is to eliminate the “clunk” sound that comes from the motor when it is shifts into gear. The clunk is the take-up of freeplay, mostly in the shifting mechanism and bevel gears in the gearcase, when thrust from the prop is initially applied. The SDS hub features a new splined rubber element that is much softer material than the previous press-in rubber hub. The splines in the rubber hub mate to splines in the prop hub, and enable the prop to rotate about 3/8-inch against the tension of the rubber before firmly engaging. This occurs when a new keyed washer tightens against slots in the hub. So instead of banging against the driveline, the prop now sort of gently “snugs up” to the prop shaft. I gave SDS a test on several boats at the intro, and it works as advertised – shifting is smooth and mostly silent.

The new Yamaha SDS prop hub system places a softer rubber element between the propeller hub and the prop shaft to cushion the driveline when the motor is shifted into gear. A keyed washer snugs against slots in the hub to provide a mechanical connection.

The new Yamaha SDS prop hub system places a softer rubber element between the propeller hub and the prop shaft to cushion the driveline when the motor is shifted into gear. A keyed washer snugs against slots in the hub to provide a mechanical connection.

Designed to be introduced with the new 4.2-liter V6 motors, the Salt Water Series II props with SDS can be used on previous Yamaha V6 models, but you have to buy the new washer and some other hardware to match the prop. Note that SDS is not a feature of the new props designed for the V Max bass-boat motors. However, Yamaha expects to spread SDS across its prop line in coming years, part of an new emphasis Yamaha says it is making on prop design and innovation since it acquisition last year of Precision Propellers.

All-new F6/F4 portables

 The new Yamaha F6/4-hp features a new 139cc powerhead.

The new Yamaha F6/4-hp features a new 139cc powerhead.

At just 60 pounds, Yamaha says its new F6/F4 four-stroke portable outboard weighs about the same as the last two-stroke models it offered in this range before emissions regulations took them off the market. The new 139cc single-cylinder F6 is 23 pounds lighter than the 197cc twin it replaces, while the new F4 is actually 12 pounds heavier than the 112cc single it replaces (the Mercury 6/5/4 models weigh 55 pounds). This is a much better motor than the old F4, however, with a CDI ignition for easy starting and a pressurized oiling system. If you’ve owned a portable four-stroke outboard in the past, you’ll appreciate the fact that these new Yamaha motors can be laid down on the port or starboard side, or resting on the rear grab handle, without leaking oil. One very cool feature is a new fueling option. You can rely on the built-in 1.1-liter tank, or use a remote portable tank plugged into a fitting on the motor. There’s a handy valve under the cowl you use to switch from one fuel source to the other. Also under the cowl is a small primer bulb that will help fill the fuel line when the portable tank is attached after a re-fill.

A new F70
This motor will replace the F75, which shared its 1.6-liter four-cylinder powerhead with the F90 and was too large and, at 369 pounds, pretty heavy for this class. Instead, Yamaha has tuned up the 996cc four-cylinder powerhead from the F50/60 and called it the F70. At just 260 pounds, the new F70 is the lightest motor in the class, weighing less than even the 320-pound two-stroke Evinrude E-TEC 75. The F70 has a compact single over-head camshaft design, and electronic fuel injection. Changes to the powerhead in its adaptation to a 70-hp rating include larger intake valves with 17 percent more area, and lighter-weight pistons. This motor also uses the lower, 2.33:1 gear ratio from the high-thrust T60 pontoon-boat motor (the F60 ratio is 1.85:1), for better acceleration and grunt on heavier boats. Anglers might consider pairing the F70 with the optional Multifunction Tiller Handle or Command Link tachometer, both of which enable an electronic trolling speed control that can be set between 620 and 900 rpm in 50-rpm increments.

Yamaha is guessing that, in a tight economy, a motor like the 3.3-liter F250 set up for cable controls will be a popular option for those who’d rather re-power than buy a new boat.

Yamaha is guessing that, in a tight economy, a motor like the 3.3-liter F250 set up for cable controls will be a popular option for those who’d rather re-power than buy a new boat.

Reprise of the F250

In a move aimed directly at the re-power market, Yamaha is bringing back a 3.3-liter V6 F250 model with mechanical shifting. Compatible only with cable-style control boxes (as opposed to the electronic “drive-by-wire” controls required with the last version of the 3.3-liter F-250) this motor makes it easier and less expensive to re-power a boat presently rigged with cable controls and either a two-stroke or four-stroke Yamaha motor. This motor does have variable camshaft timing for great fuel economy, and meets California three-star emissions regs, so it can be sold anywhere.