Cable and stub shafts

[normlee]

Any suggestions to the current best quality and availability. Bought a few flexs in the past that lengths are not quite right and square drive is sloppy. Also experiencing 7.5 stub shafts wear out real quick. I run 3.5 lawless and 7.5 K&B

Thanks!

 

[topfuel443]

In my opinion, the current 7.5 K&B flex shafts are as good as it gets. The other versions are too stiff and generally cause too much drag. 

The stub shaft bushings are something that we have fought for years and have not really ever come up with a viable solution to fix them. Luckily its easy enough to rebuild the K&B prop shafts with bushings, but they still dont last very long. we mostly just deal with sloppy prop shafts. 

If the powers that be could ever talk OS into making a 7.5 sized lower unit that is comparable to their 3.5 size, they would put everyone out of business, and I would buy 10 of them right off the bat. Hell, even if they just made an OS prop shaft that screwed into the K&B/lawless 7.5 lowers id be happy. 

 

[Carl Van Houten]

There have been a few people over the years who have made replacement stubs for the K&B 7.5 lower. Some had bearing and some had bushing inserts. Not sure why they never got very popular among racers. I bought one from Joe right before he passed but I haven't tried it yet. I think it came from Hyper Performance. The reason I have not tried it is because there is a very important undercut missing. This feature has to be included in a replacement part. The undercut actually faces up with the trailing end of the bullet and pulls the halves together when tightened up. This HAS to be included or it will trash the aluminum threads and then you have an even bigger problem.

There was a guy in SOWEGA that showed me a replacement stub that he was planning to manufacture that looked nice. It was a bushing type and if I remember right he had added about 1/8" to the bushing length. You really cant add too much length to the bushing before you start pushing the prop into the water pickup. Maybe that is no longer an issue because IMPBA clubs have gone mostly to the Super Stock class that will allow changes that the "stock class" would not allow years ago.  

If K&B would just extend their cav-plate back about 3/16"-1/4" and also move the water pickup back that same amount it would allow for a much needed additional bushing length in their stub. Doing that would cause them to have to carry both styles because the new stub would crash the prop into the pickup if used on the old lower. Here we are 35+ years later and no change.

An upgrade kit could be made that includes an extended cav-plate with the pickup moved back and replacement stub that features a longer bushing with a tighter bushing to shaft tolerance ... Gabe, make us that kit!

Heck I would want one on all my 7.5 units.

 

[topfuel443]

I already offer the Carbon Fiber Cav Plate kits for the K&B lower units. They move the water pickup back quite a bit and provide plenty of clearance. 

I also sold the bearing bronze K&B bushing assemblies (Formerly Nitro Water Sports) when I had Oval Express Racing, but they dont last too much longer than the stock K&B units. I sold that remaining inventory to John Otto when I closed down OER. I think he still has some. 

Yes, I agree with you on the back bevel being needed on the bushing, you will destroy a lower unit if that is not present. 

If I knew what alloys they use on the OS prop shaft bushings, thats what I would go with. The bushing manufacturing isnt too involved, but making the shafts can be difficult due to the blind square hole needed for the flex as well as proper hardening. That REALLY drives the cost up. And folks are cheap. The investment to return ratio just doesnt make a lot of sense. 

 

[LohringMiller]

It's tough to beat the Hyperformance units.  They last lots longer than K&B assemblies.  Their flex shafts are good as well. 

Lohring Miller

 

[Marty Slater]

undercut ?  Carl please tell us more

 

[topfuel443]

There is a back bevel on the end of the K&B style bushing that matches up with the taper of the lower unit bullet. When the prop shaft is screwed into the lower unit, the tapers match and it helps to keep the two lower halves pulled together and subsequently the fragile threads as well. 

The Hyperformance propshaft does NOT have that back bevel. It was designed to be used with the one piece design lower (The bullet drive) unit that Hyperformance also sells and doesnt need the back bevel for that lower since its not split like the K&B and Lawless. 

 

[MarkScott]

Here's the Hyperformance unit's.  The one on the right had only 6 tanks on it. How this happened is beyond me as nothing was hit.  Maybe it just can't handle the power from the Nova Rossi?  Second unit is working just fine.

 

[KENNY MUDD]

on the 3.5 lawless the hyperformance flexshafts and propshfts are the only good ones I found that work. the flexshafts are a little longer and don't strip out the square drive. Otto has some 3.5 propshafts that are nice but I have found that the new ABC props are to long for them unless you shave them down.  On the 7.5 k&b flexshafts and propshafts only way to go. The propshafts do wear out rather quick but we don't have another choice. Like Carl said, the hyperformance ones will strip out the lower unit. Once they fix that , they will be awesome.

 

[Brandon Atwell]

Ideally, stick with Lawless that is tapped for the O.S. assembly. Easily the most bulletproof setup, unless you’re talking just running an O.S. lower unit. Only way to go for 20 modified.

I’m surprised no one has “splashed” the O.S. assembly and upscaled it for the KB threads. I’m suspecting the tooling and work far outweighs the demand.

 

[Marty Slater]

so if i understand this there is no way of running the Hyperformance shafts in a KB  7.5 lower

with out damaging it?

 

[Alan Elzer]

Hyperformance units works for me. Except I seal the holes at bottom of lower unit. Then I have a oiler that supplies lubrication during a heat. This makes oil come out through prop shaft bushing area only. Pryor to sealing the holes at bottom everything wears out quickly....just my 2 cents worth.

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[Carl Van Houten]

I never did buy into the age old K&B theory that the holes in the bullet were so that the water could get in and lubricate the bushing.  :blink: Like Alan said plug those up and put an oiler on it!

That is the best setup you can have.

 

[Jim Allen]

Carl,

I'm using the stock shaft that comes with the stock K & B unit. I replace the teflon bushings in the housing with a precision machined, shoulder type, Barium metal bushing which is pressed in. The drive dog rides against the teflon washer & the shoulder type bushing. The stuffing tube is a hard brass tubing with a grease fitting. No wear or failure problems of any kind! 

Jim Allen

 

[Marty Slater]

any one care to trade for  my 2 new Hyperformance  prop shafts for 2 new KB prop shafts?

 

[Mark Simmons]

Are those 3.5 or 7.5 shafts and have you ever rebuilt them.

 

[Mark Simmons]

Are those 3.5 or 7.5 shafts and have you ever rebuilt them.

 

[Marty Slater]

they are new 7.5 Hyperformance i want new 7.5 KB 

 

[Mark Simmons]

I don't have new just rebuilt 7 5 mark

 

[Alan Elzer]

Marty. I'd like those stub shafts, think I have new k & b ones.

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