Behind-the-Scenes Tour: Pulling back the curtain on how Yamaha props are made title
process using fire to make a propellor
In my line of work I get the privilege to go beyond the velvet ropes for some exclusive tours and experience things not every boater is able to see. Okay, so “velvet ropes” might make it sound a little more glamorous than it really is. I’m basically referring to when I am invited to a pontoon manufacturing tour or I get to see first-hand how an outboard is engineered. It’s not exactly the same thing as gaining concert access with a backstage pass, but I still think it’s pretty cool.

Of all the behind-the-scenes tours I’ve been on, one of my all-time favorites was back in May of 2012 when Yamaha invited a group of marine journalists to Indiana to tour the Yamaha Precision Propeller Industries (YPPI) plant in Indianapolis. I remember being amazed at the process and truly impressed by the precision and dedication it takes to create one of its stainless steel propellers. Fast forward ten years and I found myself once again in Indiana, this time at Yamaha’s brand-new, state-of-the-art, $20 million facility that was recently completed in Greenfield.

To appreciate the journey YPPI has been on to reach this point of its monumental success, you have to go back to the late 60’s when Precision Propeller Industries was simply a service shop for all propellers. Boaters, especially those who liked to go fast, came to the founder Jim Booe to “tweak” their prop to gain more performance in their boat. As business grew, it became apparent that you could build overall performance into the original design so it wouldn’t take customization to a finished product. In the early 1980’s, PPI began manufacturing the TURBO line of propellers. The company grew through both the TURBO line of propellers as well as building propellers for outboard brands and private label retailers and distributors.

process of hot melted metal being poured to cool down
propellor being made, cooling down in a pot
propellor that's a work in progress, cooling down from being red hot
Yamaha Pairing
In July of 2008, the assets of Precision Propeller, Inc. were purchased by Yamaha and became part of its Marine Group. The investment casting manufacturing expertise of Precision Propeller combined with the distribution and product strength of Yamaha formed the ideal partnership. After shedding all other product lines except Yamaha propellers, the company was renamed Yamaha Marine Precision Propellers, Inc., and has continued to build and grow the business ever since.
Modernizing The Process
On my tour of the new YPPI facility, which is one of the newest investment casting foundries in North America, the differences between the two plants were endless as Yamaha has truly invested in its future by creating a more refined process of manufacturing props, while maintaining its dedication to precision.

The 55,000-square-foot plant began operation in March, 2021 and YPPI designs and builds stainless steel propellers for distribution around the globe for Yamaha Outboards to fit thousands of different boat applications in the market.

While all Yamaha polished stainless steel propellers are cast at the new Greenfield facility, they’re actually finished at a YPPI facility in nearby Indianapolis. With a combined 200 employees, the YPPI facilities in Greenfield and Indianapolis operate three shifts five days a week. In total, YPPI manufactures more than 300 different propellers and we were able to witness the process each step of the way.

saw blade being used and sparks flying
melted metal being poured into a propellor
person wearing a face covering in a warehouse while working on a propellor
person wearing a face covering in a warehouse while working on a propellor
person wearing a face covering in a warehouse while placing a propellor into a machine
person wearing a face covering in a warehouse while working on a propellor
close up of a hand working on a propellor
workers in a propellor warehouse
Investment Casting
Yamaha’s stainless steel propellers through modern technology are created using the investment casting process, a metallurgical art that dates back more than 4,000 years. Investment casting, also known as precision casting or lost-wax casting, is a manufacturing process in which a wax pattern is used to shape a disposable ceramic mold. A wax pattern is made in the exact shape of the propeller to be cast. This pattern is coated with a refractory ceramic material then molten steel is poured inside to create the propeller. That is the simplified definition; the process in-person is something I wish everyone could get past the velvet ropes to see for themselves.
We’re seeing a lot of manufacturers from all industries transitioning to automation these days and this is exactly what Yamaha is doing with its new facility to improve quality and accelerate production. According to Yamaha, they’ve been able to go from 60,000 props per year before the Greenfield location opened to more than 100,000 pieces today. That’s quite a difference in volume and is greatly appreciated when as a retail customer you’re trying to wait patiently for the new prop you ordered to arrive.

As you probably expect, automation also results in tighter manufacturing tolerances, which reduces the amount of finish work each prop requires.

robot arm applying a coat to propellors
propellors with a coat dripping off of them
robot arm holding multiple propellors
propellors being hung to dry after a coat was applied
tour of a warehouse where propellors are made
Amazing Molds
One of the sections I found most intriguing on the tour was the wax replica, or pattern, of each prop that was made. Once formed, the application of refractory material around the wax pattern is performed by placing groups of five on conveyor belts with robotic arms doing the dipping.

Without going into too much detail, a fine zircon sand is used for the first coating that preserves the details of the pattern including the logo on the prop barrel. A robotic arm first dips the mold in a zircon slurry and then places it in a rotating drum of a rainfall sander that sprinkles zircon sand that clings to the slurry.

There is a drying process between each of the five coats with each coating using a coarser silica sand each time. This process takes about 24 hours and when complete the refractory material is extremely thick around the propeller pattern.

Melt & Pour
Thanks to an 1,800-degree oven, the wax is then melted from the mold, leaving a hollow shell where an automated handler moves it into position for the pour. Next, the 3,000-degree molten stainless steel is poured. The pour is fully automated so the precise amount of steel is poured for each prop size. The shell then moves down the line and is covered with a lid to control the rate of cooling.
Still Growing
The last step of grinding and polishing the props is done at the Indianapolis plant, but Yamaha is already making plans in the near future to bring everything together in one location with an expansion on the Greenfield building. The plan is to accommodate a new automated grinding and vibratory polishing process which is currently done by hand. Hopefully it won’t take another ten years before I’m invited back for my next YPPI tour.
For More Information