Things to Know

PROP REPAIR & MODIFICATIONS

Mark’s High Performance Propellers and Hydromotive Engineering Co. would like to clear up some misunderstandings in regards to propeller repair and modifications to Hydromotive propellers. Mark’s High Performance Propeller does repair and modify some of Hydromotive’s props when Hydromotive is overloaded with work, so as to get the work out to their customers in a timely fashion. All work sent in by Hydromotive has work orders attached to the props specifying the exact details of work to be performed by Mark’s High Performance Propeller. In no way does Mark’s perform any work to props sent in by Hydromotive, other than the work specified on their work orders. Mark’s does spec out work for their customers only, and not Hydromotive’s customers.

Hopefully, this will clear up some of the confusion and rumors flying about in regards to the relationship between Hydromotive and Mark’s. Since Mark used to work for the foundry that cast Hydromotive props, it was only logical for Hydromotive to send their overflow work to him.

METAL ENHANCEMENT OF HYDROMOTIVE PROPELLERS

Hydromotive Engineering has introduced a new proprietary metal processing technique to greatly enhance the fatigue resistance of our stainless steel propellers. As most of us know, propellers generally have adequate blade strength to handle the peak bending stresses that are encountered in very demanding applications from high horsepower and torque. Unfortunately, many propellers cannot handle the high frequency stress reversals imposed upon the blades as a result of high ” X ” dimensions, and aerated step bottom boats and cat boats. In these instances the blades are subjected to loads that bend blades fore and aft many times each minute as the blades enter the water and exit the water each revolution. This continual flexing back and forth weakens the blades, leading to cracks and eventual loss of the entire blade. Any knicks on the leading or trailing edges of the blade will exacerbate the problem. If you bend a coat hanger back and forth enough times it will eventually break. If the hanger has a knick in the bend area, it will break much sooner. Most of our customers do not check their props for small knicks and lose blades as a result. Blade thickness also will reduce the ability of the blade to survive the stress reversals. With our new metal processing technique thin blades will last much longer.

The new metal processing technique we currently employ at our customers request requires a lead time of 4-6 weeks at a cost of 315.00. The end result is a prop that can handle up to ten times the stress reversals of anything else on the market. This includes exotic alloys used by some manufacturers. If you are interested in this technique, please contact us at 330-425-4266.

THINGS TO KNOW: THE PROS AND CONS OF BLUEPRINTING/ LAB FINISHING PROPELLERS

As a company, we are often asked about the benefits of lab finishing or blueprinting propellers. We offer the following information in an effort to enable you to weigh the advantages and disadvantages for yourself and make an informed decision.

Both lab finishing and blueprinting refer to the process used to insure the accuracy of the propeller rake angle, pitch, progression, pitch variation and cup. This hand process involves thinning the blades and sharpening the leading edges.

The advantage of blueprinting is that it reduces the horsepower required to turn the propeller and generates more usable horsepower for thrust. On an accurate, well-built propeller the speed gain may be 2-3 miles per hour. On a lesser quality propeller, the increase may be 3-4 miles per hour.

The disadvantages of this same thinning and sharpening are greatly reduced blade strength, fatigue resistance, and being more subjective to stress risers occurring at the sharpened leading edge. A sharp leading edge is very prone to minute nicks which create stress risers. These stress risers often propagate cracks that originate from the nick at the leading edge and work their way through the blade. The same thing is true for any nicks at the trailing edge. It is for this reason that we at Hydromotive grind our trailing edges from hub to tip rather than across the blade, thus eliminating any potential stress risers. Reducing the blade thickness from a 1/4″ to a 1/8″ (1/2 the original thickness) does not reduce the strength by 50%, but actually reduces the blade strength to 12% of the original. Consequently, we can not warrant any propeller that has been lab finished or blueprinted.

Cost is yet another factor to consider. Hydromotive Engineering offers blueprinting to our own propellers as well as those of our competitors. Some of our competitors are currently charging 50% more than Hydromotive charges for the service.

No matter which source you choose, we encourage you to carefully weigh all the factors when deciding whether to have this enhancement performed. Keep in mind that blueprinting, no matter by whom it’s performed, voids the warranty of any propeller.

If you decide to proceed with blueprinting by Hydromotive Engineering, it’s as simple as shipping us your propeller via UPS, or whatever means is most convenient for you. Please expect approximately a two to three-week turnaround, with seasonal delays possible.