Tuesday, August 31, 2010

New boaters are good

We've seen this all year, but the last couple of days they seem to be coming out of the woodwork:

New boaters!

New boaters are good for anyone in the marine business. They're smitten with their first boating love and they're eager to have a good time. They're spending money and ready to be educated.

In the propeller business, that means lots of educating. The main thing we need to tell newbies is that there isn't some big giant magic book that tells what prop should be on each individual boat. Using charts and good ol' fashioned experience we can suggest a place to start, but in most cases there's already a prop on the boat. Knowing how that prop runs--especially max rpm at full throttle--we can determine whether the current prop is right, or if a change is necessary.

Propeller damage is another thing. Bottom line is that any damage will compromise performance, especially fuel economy. Best to handle minor damage before it gets too bad. And best to get a decent prop fixed at a certified propeller repair shop. Many boaters don't know that a repaired prop (especially from our shop :-) is as good or better than new.

So I'll try to be patient, as I teach Propeller 101 for the millionth time. But I need boaters to have good information about their boats--and some disposable income.

Friday, August 27, 2010

And another Yamaha thing . . .

We hear from lots of customers who buy the wrong props (from somewhere else) for their Yamaha 60-130 hp series outboards. They have a 17 pitch aluminum, or OEM stainless, then buy an aftermarket prop of the same pitch. Then they lose lots of rpms and performance.

The reason is that the OEM style props are semi-cleaver designs with very little cup. They are easy to turn, and typically have less rake and cup than an aftermarket prop. You can identify them by the straight trailing edge. The stainless OEM props are painted black. A "normal" aftermarket prop, with more rake and cup, will usually turn less rpms. It's most common with stainless propellers.

When replacing an OEM style prop, we'll make sure we sell the aluminum prop from Michigan Wheel or PowerTech (pretty much identical to OEM) or an OEM-style prop from PowerTech (the SCD style). That will provide performance like the customer is used to. If the customer insists on an aftermarket style (for price, or to use a replaceable hub kit, like the Flo-Torq), we'll drop a couple inches of pitch.

This is reason number 1000 to talk to a prop shop before you buy a prop. Internet buyers, beware!

Thursday, August 26, 2010

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.