Yamaha propeller hub problems

Yamaha appears to be having some problems with its V6 motors prematurely and repeatedly "spinning" rubber hub propellers. It's been going on for years and now it seems to be coming to a head. Google "yamaha hub problem" and you'll see the litany of complaints.

Most modern propellers use a pressed-in rubber hub bushing to transmit horsepower to the water while protecting the drive train. The rubber bushing, with a metal splined piece in the middle (vulcanized to the rubber) that slides onto the propeller shaft, helps cushion the drive train from the strain of shifting and underwater collisions. Over time the bushing wears out and fails, or "spins." The boat revs up and won't go anywhere. Usually the boater can limp home at idle.

So rubber hubs have always been a bit of a pain for prop shops and boaters, but the recent surge in horsepower and engine heat has created a huge problem--rubber hubs have simply been melting and failing very prematurely. Mercury recognized this problem about 10 years ago and introduced the Flo-Torq II hub system, a delrin drop in bushing that shields the drive train but is relatively impervious to heat and horsepower. Other propeller manufacturers have followed suit with products like the PowerTech Cushion Lok, the Michigan Wheel XHS hub and the Solas Rubex, to name just a few. These hubs aren't perfect, but they hold up much better than rubber hubs.

Yamaha has stuck with the rubber hub system, but their new motors, especially the four strokes, generate tons of torque and, anecdotally, lots of heat. The motors even include a special scoop on the trim tab to feed cool water into the exhaust housing.

For many years we and all prop shops used aftermarket hubs from a company called HMS to replace failed hubs in propellers for these Yamaha motors. But in recent years, large shops like ours started seeing multiple repeated failures. We and others started talking to Yamaha, and they made available the OEM 61A hub used at the factory, which was never before made available as a service part. We found slight but apparently significant differences between the two hubs, because when we tried them we had very good success. Very few comebacks. So Yamaha agreed to make the hubs available to prop shops.

This was about a year ago. Since then, we have received about 50 hubs from Yamaha and could have used that many more. We have props lined up to be rehubbed. I know other shops are in the same situation. Yamaha cannot tell us when we'll get more hubs.

To Yamaha's credit, they have worked with prop shops on this issue like they've never worked with us before. And they're introducing a new hub design, the SDS, that should solve this problem going forward. But it won't retrofit in existing propellers, which means this issue won't go away anytime soon.