P Spec Tunnel Lower Units

As in all things it comes down to preference and opinion. Not necessarily that one is "better" than another, but what would be your preference of a lower unit for a P Spec Tunnel and why? K&B, Lawless, OS, Hyperformance angle 3.5, Hp Bullet or some other?

I'd be interested in your thinking & opinion.

Kelly

For me it's the cut down leg from BBY: http://bbyracing.com/elechardware.htmIt comes highly polished, a thing of beauty really and very easy to hook a motor to. To my knowledge it is the only dedicated electric leg currently produced. Randy from BBY also uses and recommends the Hyperformance 3.5 bullet drive: http://hyperprod.bizhosting.com/3_5_bullet_drive.html

So to answer your question, for a p spec lower, my #1 choice would be the BBY cut down leg, followed by the hyperformance bullet. You'll probably find a lot of people say go with O.S. because it's easy and available and because of its "better flex shaft", but I've found them to be the most underperforming leg besides the Thundertiger leg. I've been told (and have confirmed through experimentation) that the K&B flex shaft is a better flex shaft because it bends easier and has less resistance. I like to be different and go for the better leg instead of the same old O.S. leg. As far as Lawless, I think it's worlds above everything else and is the only leg I will use for a mod nitro. That being said I've never used one for electric because I've been perfectly happy with the BBY leg. I haven't officially been to any races and am relatively new to this hobby so take what I say with a grain of salt. That being said I have recently done a lot of experimenting with different legs and have contacted and learned from a lot of experts and am relaying much of their information. Hope this helps

Hey Randall - thanks for the input. I notice that the BBY Racing unit doesn't use a cavitation plate. Is that working well for some of you?

Kelly

I haven't noticed any effect from the lack of the cav plate. Maybe others can chime in. Only thing is you'll have to modify the leg if your want a water pickup. Personally, I don't use a water pickup.

On my O.S. lower, the cav plate is 1/2" wide carbon fiber sheet. Only reason it's there is to get the water pickup behind the prop. I am using the O.S. as it came with the package that I purchased. It's my first EP tunnel. May have to look into the BBY lower if I make another boat. There are a few suppliers of replacement flex shafts. Lawless or Chris Flynn come to mind. Chris has a sweet looking O.S. lower that has been altered to get the motor lower than the stock position.

Okay...I can appreciate all the effort that people have put into designing building and marketing alternative lower units and there needs to be as much diversity as possible in this sport but, if we are trying to validate one product over the other let's not forget what lower unit holds the current record for being the fastest 2-lap outboard in the world, ever, of any size outboard tunnel boat or any size outboard motor / engine combination.

The lower unit that holds this record is the Lawless with a blistering 2-lap time of just over 22 seconds.

-Carl

Carl, I agree the Lawless is an amazing drive, which is why I said it's the only one I'd ever use for a nitro outboard (though the Hyperformance angle drive is a pretty appealing drive for nitro as well). In fact with any luck my Lawless 3.5 drive with the NR KEEP on top will hopefully become the fastest outboard in existence on my JAE OB outrigger. Well with a lot of luck really but I'm receiving a lot of help from a lot of people. One of them being Fred Howe from Lawless Drives, who's service is unbeatable, and who without I would not even be attempting an outboard record.

I decided to attach some pics. One is my Lawless with the NR, the other my BBY outboard leg where I threw on an old brushed motor just for show. I also have a side by side comparison of the two drives plus a screenshot I took of Kris Flynn's modified Lawless unit to accept a motor.

For electric I still like the BBY leg over anything. It's minimalistic, purpose built, and performs very well. All you have to do is throw on a motor and connect it to the flex cable with an Octura electric flex hex.

Carl Van Houten said:

The lower unit that holds this record is the Lawless with a blistering 2-lap time of just over 22 seconds.

-Carl

Click to expand...

And 6-Lap Heat Racing Record.... And P-LTD SAW Record... And 2016 National Championship in P-LTD...

Just sayin'. Could just be a fluke I suppose...

For FE Outboards, I've seen decent results with the O.S. units, and the Bullet Drives, in addition to the 3.5 Lawless. The Lawless is, however, lighter, and more "minimalistic", that either of those.

I would stay away from anything plastic for serious racing. The skag flexes too much at speed. And I still think it's more about matching components than it is the individual components themselves, and then setup.

I've run K&B, REK, O.S., and now the Lawless, and now will only run the Lawless. Why mess with something proven to, well, be the best, thus far??

Each lower has its own handling quirks. knowing this I am looking for other factors.

I like a nice meaty skeg.. I can Massage it to what I want.. I also want it parallel with the stub.. which the K+B is not..

As we all know.. the stub on the K+B is not all that great..

K+B is out for me.

I have raced the Lawless and had good luck with them.. With the added benefit of adding a OS stub.. this is a plus… Price.. its OK.. and Fred is a nice cat… all good…

BUT.. I don’t much care for the motor mount so.. although its good I will again pass on this one.

I have owned and raced a few others BUT.. to me.. dollar for dollar the OS IS IT. The motor mount alone pushes it over the top for me..

From the stub to the skeg to the motor mount to the durability of the parts… it’s a GREAT choice.. and to add, I PERONALY don’t give one rattle snakes bottom about records, SAW OR OVAL.. I like heat racing… the OS lower unit has won THEM ALL at races around the world since 1997.

Grim

The times I've been to races (as a spectator which will hopefully change soon!) it'd be about impossible to find anything other than the O.S. leg. In other words by numbers the O.S. leg would have to truly suck for it to not win all the time. Ask people what they used to break a speed record and one thing's for certain: it ain't gonna be an O.S. leg despite the fact they are so abundant. I decided to be scientific and test multiple legs on the same setup to determine what I wanted to use for my SAW attempts for B O/B hydro and N tunnel. I noticed that the BBY leg was superior at around half throttle, the Lawless leg was superior pretty much at any rpm, and the Hyperformance bullet really preferred higher rpm operation. This was with a brushless motor at 22.2V. The best I could describe the O.S. leg was a lethargic version of the Lawless drive; the underperformer in my test. So for me this tells me I should use the BBY leg for my N tunnel record attempt (and that it would be a great candidate for P-spec) and that I should use the Lawless for my Hydro record attempt. I don't mean to go against the masses, especially with my lack of experience in racing (nonexistent experience compared to the Grimracer himself) but I truly believe my test was somewhat valid and hopefully enlightening

The Hyperformance Prod 3.5 K&B replacement stub takes care of any deficiencies that the Lawless with K&B sized stubs may present. With the benefit of having less "bulk" down at the waterline.

But, like I stated above, I don't believe any ONE lower is THE lower. I just keep using what's worked for me.

I have run every lower mentioned here other than the BBY which looks to be a K&B rework with the skeg cut shorter than I would like. Lawless is a great piece of machine work but the metal bends with impacts. The skegs are thin and can bend and flex. In my experience they don't hold up over a couple race seasons as well as the OS. The OS has the best mount and has a stronger skeg that can be shaped to your liking. As for the actual prop shaft the OS is the best, period. If you have something that's working for you stay with it. If your new or don't have machining capabilities the over the counter OS is a great buy.

Mic

Randell.. Great post. When you have a clear objective, have done the testing, and confidently report the findings. Its clear your results will be good.

Good luck and keep us posted.

Grim

Grimracer said:

Randell.. Great post. When you have a clear objective, have done the testing, and confidently report the findings. Its clear your results will be good.

Good luck and keep us posted.

Grim

Click to expand...

Grim, thanks! Next I'd like to test powerheads side by side with the same setup, but that would cost quite a bit more and plus I don't have any experience modifying powerheads. Another thing, and this is something I learned from John Otto at Technology Hobbies- the K&B/MECOA flex shaft bends easier, has less resistance, and your engine will like it better. John told me he's seen O.S. engines running like crap run good with the K&B flex shafts put in. Well, I have a Top Speed 2 with an O.S. max water-cooled outboard that never seemed to run right, and sure enough when I threw a K&B flex shaft in there it ran better. Also quick shoutout to Darin, I agree with you on the Hyperformance stub. I don't know why people say the O.S. shaft is the best especially with all that bulk, has anyone ever had issues with the Hyperformance stub?

I have been at this some time.. John has been at it longer... he is a good guy.

I have never had a bad OS Flex Shaft.. not out of the bag or causing a performance issue.

I have never had a bad OS Stub Shaft.. not out of the bag or causing a performance issue.

I also however understand that "stuff happens" so I suspect someday I will get one.

I HAVE had a bad K+B Flex Shaft (I have one here.. the square does not run true with the shaft)

I HAVE had a bad K+B Stub Shaft. (I have had them shear a pins.. one run)

Having said this.. where do I place my trust..

Grim

Isn't the K&B flex shaft shorter than the O.S.? Maybe not enough to cause an issue.

JD

I us the K&B lower

Works good for me.

Sent from my iPhone using Tapatalk

Jerry Dunlap said:

Isn't the K&B flex shaft shorter than the O.S.? Maybe not enough to cause an issue.

JD

Click to expand...

K&B makes a flex shaft just for the O.S.

*edit* here's a link for convenience: https://mecoa.biz/shopdisplayproducts.asp?catalogid=2424

You can get the motor lower to the water on a Lawless than you can with the OS.

I love them both when partnered with an OS stub shaft! Would not tough another K&B stub shaft with a 10 foot pole (but for 7.5 we kinda have to still)

Oh yeah, lawless has the fastest unofficial speed at around 82MPH also