Outboard Expert: Yamaha SDS Prop Hub
Innovation takes the "clunk" out of shifting gears at Yamaha.
In January I wrote about the Yamaha Shift Dampener System (SDS), a feature of the new Saltwater Series II props offered for the 4.2-liter Offshore outboards, but felt that that report was incomplete because Yamaha didn’t have a good photo of the hub design, and I didn’t have a chance to take one at the media event. But now I have that image, because Yamaha brought a propshaft with the basic SDS components attached to a test session it hosted last month in Georgia. If you didn’t quite get the SDS premise before, these photos might help.
SDS serves a purely aesthetic purpose – to eliminate the “clunk” sound that is the take-up of freeplay, mostly in the shifting mechanism and bevel gears in the gearcase, when the motor is shifted into gear. The SDS hub features a splined rubber damper mated to splines within the stainless steel prop hub. The rubber damper, which is a softer material than was used in previous prop hubs, acts like a torsion spring and allows the prop to rotate about 3/8-inch before engaging a keyed washer against slots in the prop hub. When thrust is initially applied, instead of banging against the driveline the prop now sort of gently “snugs up” to the prop shaft. No more clunk.
As I mentioned, this is a cosmetic enhancement. Yamaha says SDS does not enhance gear-train durability. Outboards have always smacked into gear, but as the motors have become quieter and quieter, that clunk has sounded louder and louder. These motors are supposed to be refined. Motors that go clunk don’t belong on a $250,000 boat.
For now, Yamaha is offering SDS only on the Salt Water Series II in 13-inch to 23-inch pitch, which were introduced with the new 4.2-liter V6 motors but can be used on previous Yamaha V6 models with the separate purchase of the washer and some other hardware to match the prop. Yamaha says SDS will become a feature of its other prop lines in the future.
- Lenny Rudow is Senior Editor for Dominion Marine Media, including Boats.com and Yachtworld.com. With over two decades of experience in marine journalism, he has contributed to publications including Boating Magazine, Marlin Magazine, Boating World, Saltwater Sportsman, Texas Fish & Game, and many others. Lenny is a graduate of the Westlawn School of Yacht Design who has won 28 BWI and OWAA writing awards.
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Tags: propellors, Yamaha SDS