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prop hubs

Old 02-29-2004, 06:10 PM
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Question prop hubs

My prop is in getting reconditioned and the tech there told me to replace my steel hub piece with a plastic one. I know if I hit something it will act as a shear and probably save my drive but I am worried that it won't last long or it will slip. I have a 502 mpi single on a 28 Stryker....It isn't that I will be going offsore racing but I wonder if the steel hub is there for a durability reason. Should I take his advice?
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Old 02-29-2004, 11:32 PM
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Default EITHER WAY

Plastic insert or stainless are super strong ,usually with 500 hp and more use the stainless insert it is more durable,even though we have seen many bent prop shafts ,with props using the plastic insert,and the prop was destroyed .But the plastic insert was fine no cracks nothing,
I, say plastic? I, do not know what the real name is or the material is?? but it's super strong.

I would use the plastic and carry a spare insert with you,and see how that does before going to stainless inserts.
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Old 03-01-2004, 06:55 AM
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Alter ego,

Mercury recommends the solid insert for application above 400 hp. Technically your engine meets this requirement so that's why it was equipped with a solid hub from the factory.

There are many factors that influence the load on a propeller hub, some of which have as much impact as the horsepower of the engine. Weight of boat, water conditions, prop pitch, # or blades, prop material, driver style, engine torque, etc.

If your driving style is conservative you may find the plastic hub to be adequate for your needs. It will provide a margin of protection not available with the solid insert. I would recommend trying a plastic sleeve and if you shear it just put your solid one back in. You motor has a rev limiter in it so engine damage should not occur if the sleeve sheared.

The plastic hub will not "slip". What typically happens when the plastic sleeve shears is that the aft adapter spins inside the sleeve. This generates heat which melts the plastic. After you pull back and the throttle and put the shifter in neutral to figure out what just happened the water cools the plastic and it hardens. The plastic is usually hard enough, after it cools, to allow you to idle your boat to a safe location.

Matt
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Old 03-01-2004, 08:17 AM
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I'd hate to admit it, but I ran a plastic hub this past year. 580hp with a very high x-dim. It still looked like new.
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Old 03-01-2004, 09:03 AM
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I've been in a boat that sheared a plastic one. Boat had twins, and would not plane on a single engine. I suggested that he use just enough of the "spun" motor to help and the boat planed just fine and ran at fast cruise. Any more and it would freewheel though. Got us back home though.

(by the way, I carry a cheap aluminum 17 pitch prop as a spare. My boat also won't plane on a single motor with the big props, but the 17 will pop it right up and run it almost 45mph. I figured this out the second time I blew a drive and had to run 5mph for 3 hours...)
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Old 03-01-2004, 01:44 PM
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Good point. This is often overlooked by those with twin engines. Just because you have twin engines doesn't mean you can get the boat on plane with just one motor.

For those of you who travel offshore many miles having a spare prop of a lower pitch is a great idea. Put the lower pitch prop on the good motor and off you go. If you have a twin with Bravo 1 drives you only need one prop. A 17 or 19 pitch prop should work fine.

If you have an outboard or Alpha drive twin with counter rotating drives you need to carry a left and right spare prop. A great choice for this application is the Mercury or Quicksilver 4 blade aluminum prop. These are available in both left and right hand rotation in 16,18 and 20 pitch. They are relatively cheap and use the same Flo-torque hub parts, if you have a Flo-Torque hub system prop now. This prop will even work if you have the large shaft on XR/XZ drives.

Matt
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