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Yamaha Propellers Losing Blades

O

OBDoctor

New member
We have a customer with a Yamaha VF225LA SHO VMAX engine that keeps breaking blades on the propellers. They purchased the engine last January (2017) to repower a 2010 Ranger 2050 Reatta. The dealership installed a 20" motor on a 25" transom, so they have to lower the jack plate all the way so that it will work. In the 13 months that they've had the boat, they've slung a blade off of 4 props, and spun the hub out of a fifth. The blades have all cracked on the trailing, cupped edge right at the hub. The props have shown no evidence of striking anything. The propeller that was originally installed, and that we've used to replace it, was a MAR-GYT3B-V6-22 Stainless. Does anyone have any ideas as to what is causing this? Should they be using a different propeller? If it was just one prop, I'd say it was just a manufacturing defect. But, to have this many failures in such a short period of time. Any help that can be provided will be greatly appreciated.

Thanks,
Harold
 
Strange indeed. First Im hearing of such an anomaly. Needless to say but worth mentioning, why purchase a boat whose engines shaft length differs from transom length. Be that as it may, this isn't the cause of cracked prop blades. Applying what I know of physics, apllied force to the blade is the only reason I can think of as being the cause. The obvious and most applied force in this case is blunt force, as in the blade striking an object. Excessive torque could also be an applied force, but in this case the engine is not capable of producing enough torque and the liquid the prop turns against is not dense enough to cause enough stress on a stainless steel prop to fracture a blade.

All of the above doesn't answer your question. Just applying simple logic to your scenario. Which leads me to ask, what has you convinced the prop has not been fractured due to blunt force?
 
My belief about the wrong engine shaft length is that the dealership had the engine in stock, and decided to use it. Or, they ordered the wrong shaft length, and installed it anyway. Our customer has owned the boat since it was new. The boat originally had an ETEC 225HO on it, and it lost a powerhead with over 2000 hours on it. They never had any prop trouble with the ETEC engine. The failed props have had no damage to them. No marks, dings or dents anywhere. They looked just like they did when they were new. Just missing a blade. 2 of them still had the failed blade hanging on by about an inch of blade. That blade showed absolutely no signs of striking anything. In my 40 years in the business, I've only seen a few props lose a blade. After replacing the prop, the customers never had another failure.
 
Where is the anti-ventilation plate in relation to the surface of the water when the boat is running on plane with the motor trimmed up normally? Can you take and post a photo?

What you are experiencing is not normal. Completely abnormal. Most will never throw a blade in their lifetime. For someone to throw 4 is indicative of a problem. I am guessing it has to do with the engine mounting height. Being the wrong motor for the boat.
 
This is a common problem with a motor running to high as the blades "slap" the water and crack. Also bad casting will do this. The over hub props are really bad about this, as I went thru 3 Triton props $600 ea before I got a good one. I now have any HP prop x-rayed
 
Thanks for the information. We've told the customer to take the boat back to the dealer that installed the motor & make them rectify the problem.
 
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