Prop Shaft

[FLATS ONLY]

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The 2 most recomended and used shaft materials are Aquamet 22 and K Monel. In high HP boats I will only use K Monel. In my DiMarco 21 with a projected 2500 HP it will be getting an 11/8" shaft of K Monel. With the source of these materials coming into play because of all the cheap shit coming out of China, you have to be extremely dilligent when sourcing a supplier. At this year's Enduro there were 4 propshaft failures all new shafts and all from the same supplier. 3 were material failures and 1 was caused by a thrown propshaft blade. All were 1" Aquamet 22 shafts. There are only 2 K Monel manufactures and/or distributors in the US and their base material is sourced from China. The GOOD K Monel shafts come from Italy and are made totally in Italy but are very pricy at about 1800.00 for a cruiser length shaft. Cheap really if you are running a Grose prop!!!! Whip struts, forget about it! Drag boats, 1" shaft, K Monel if you love you're prop. BAF, BAH,BFH 11/4" at least K Monel. I had a strut failure in my DiMarco 21' going 100-mph with an 11/8" K Monel shaft that was off of one of Sonny's race boats orignally and after about 15 years running it. It tried real hard to router it's way thru the bottom of the boat but got everything under control and idiled the boat about 2 miles back to the ramp on the Delta. That shaft was only bent from the strut end back and I still use it today to bore propshaft holes in the bottom of new boats and the prop suffered no damage whatsoever!!!!!!! My 2 fingers are tired again, time to move on1

They were not all failure of material. Installing propellers & making correct keys for each prop is what's important. Installing the propeller correctly is where it's at.

[gn7]

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They were not all failure of material. Installing propellers & making correct keys for each prop is what's important. Installing the propeller correctly is where it's at.

I heard as well that Gary H shaft failed due to the prop not being installed properly. However, Gary did fail a shaft the year before towards the end of the race. You don't go that long with that kind of power with a prop installed incorrectly. That said, there is ALOT to be said about the fitment of a prop on the shaft. If the prop is too dependent on the key to control rotation, it is going to be more prone to failure at the shaft, and even the prop hub than if the taper takes the brunt of the load.
Husky motorcycles for decades use a tapered shaft with no key for the front sprocket. You could break chains, blow clutches and transmissions, with all the hammering of a motocross or desert race and never move that sprocket on that tiny ass shaft. Get wrong, the shaft would be a scored POS in no time.
Way too many people over look the benefits of lapping a prop to the shaft too greatly increase the holding power of the taper, and get the load off the key.
The Bloodshot Schiada just had a shaft diameter not up to the task, as well as have may extended to far from the shaft in an effort to get to carry the nose.

I never bought into the idea the material was at fault. AQ22 has been used too long to blame it, unless someone could prove the material was something other than AQ22.
I will agree with Westeraero that improper machining methods can wreck havoc on the best material you can buy. If you start looking at the machining as being every bit as important as welding some exotic material, and you should, then you will become a little more conscience of how your shaft is made.
I have always got my shafts from Bob at Glenwood, and had excellent luck with them. I will give a lot of thought to where my next one is made.

Output shafts, prop shafts, and props have been the number one killer of the inboards in the Parker enduro since day one. In one year, it was 3 output shafts, including ours. There is one common thread in these boats that is overlooked as well. In a GN race the engine is primarily operated well above peak torque and deep into peak HP RPM. In the enduro, many of the engines are being operated too close to peak torque in a effort to reduce fuel, and "save" the engine. IMO, its a mistake.

[SnoC653]

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They were not all failure of material. Installing propellers & making correct keys for each prop is what's important. Installing the propeller correctly is where it's at.

That makes a lot of sense. Where parts join and torque is transferred can easily become failure points. Improper fit would just increase those stresses.

The keyway concern was discussed but may be hard to find until HB cleans the thread up.

[HotWater]

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They were not all failure of material. Installing propellers & making correct keys for each prop is what's important. Installing the propeller correctly is where it's at.

Maybe we can get this back on track.

Lapping the prop to the taper and making sure the prop seats on the taper the same depth with or without the key are the only things I know of for proper install. What are some other steps to be taken?

[gn7]

Maybe we can get this back on track.

Lapping the prop to the taper and making sure the prop seats on the taper the same depth with or without the key are the only things I know of for proper install. What are some other steps to be taken?

Once the machining is done, there not much you can do aside from lapping it. The main thing is trying to get maximum contact on the prop barrel, and some props are not machined the best, both in taper angle or surface finish. I've had to bypass props that the barrel was too wavy to get sufficient surface area and the barrel diameter was already bored to near max diameter

[ogshotgun]

Maybe we can get this back on track.

Lapping the prop to the taper and making sure the prop seats on the taper the same depth with or without the key are the only things I know of for proper install. What are some other steps to be taken?

on the TFH i help with , we lap the prop to shaft with 180 grit compound , till we achieve at least 80% plus contact , than we clean everything, make sure the keyway has room to move lengthwise a little , if its wedged solid it cracks the hub, just our experience, than we use red loctite and coat the shaft than install the washer, main nut torqued to 200, than jam nut at 125 pounds, after each pass the props and shafts come out , the prop is welded to the shaft and a real nightmare to get off,after that the process is done again , and again till we see tiny cracks starting to appear , than its junk, also new prop on new shaft never used with any other shafts there now a set. also on this boat we have a left and right , turning away from each other and the right prop seems to weld harder than the left prop.oh and they are Aquamet22

[Sharp shooter]

on the TFH i help with , we lap the prop to shaft with 180 grit compound , till we achieve at least 80% plus contact , than we clean everything, make sure the keyway has room to move lengthwise a little , if its wedged solid it cracks the hub, just our experience, than we use red loctite and coat the shaft than install the washer, main nut torqued to 200, than jam nut at 125 pounds, after each pass the props and shafts come out , the prop is welded to the shaft and a real nightmare to get off,after that the process is done again , and again till we see tiny cracks starting to appear , than its junk, also new prop on new shaft never used with any other shafts there now a set. also on this boat we have a left and right , turning away from each other and the right prop seems to weld harder than the left prop.oh and they are Aquamet22

Just curious, but how did you end up on the team and how long have you been helping them?

[gn7]

the right prop seems to weld harder than the left

That's interesting.

[gn7]

That and I thought the problem child boat was using those parabolic shaft ends and props.

I don't know that they are using them. "What A Tomato" is.

[ogshotgun]

Just curious, but how did you end up on the team and how long have you been helping them?

i have helped the team in all the local races , havasu, phoenix for last season and this season i started full time with the first race, there prop guy Charlie , has conflicts in his schedule, he will be training me at havasu and wheatland , after that i am on my own..hes the best teacher and so is eddie both highly professional and very detailed , just like my self lol