Oh Yeah!!

Hey Guys,

I've got a K&B 3.5 outboard that I have been powering a Little Lightning Tunnel hull with for years. I've been using the stock K&B prop that comes with the engine and was wandering if a Octura X440 would be a good "step up" prop for this application?

Thanks,
Phil

Jerry Dunlap

Yes. The M440 is also a good choice.

JD

Nitro boater

Try a prather 230,it works realy well.

jetpack

My Feedback: (1)

I dont think a 230 prather fits under my cavitation plate, are you cutting down the tips?

Dan S

The Prather 230 would work on the 7.5 but the 215 would work.

Dan.

piper_chuck

My Feedback: (12)

Ditto.

Oh Yeah!!

Thanks Guys!!!

jetpack

My Feedback: (1)

I thought I remembered right. When I was testing props there was very little difference between my 215 prather and my X437. The X440/3 seemed to pull the best and turn really well for me. The X442/3 took the whole straight-away to reach top end and would sag too much in the corner, plus the engine was getting too hot so I had to back down to the 440/3. The 215 would be a great prop for the older style I think. I'm using the SS with stock muffler can @ 40%.

Oh Yeah!!

Hey Guys,

I've installed the Octura X440 on my outboard prop shaft. I'm just a little concerned about the clearance between the prop and water pickup tube. If I wiggle the prop shaft a little, there doesn't seem to be enough play to rub the WPTube. Is this alright?? (see pic on left)

What is the difference between the X440 and the M440 props?

Also, compared to the original K&B prop, the X440 has a lot more blade area.(see pics) The original prop did quite well with the tunnel I was using it with, but what can I expect with the X440 prop?

Thanks,
Phil

Sean Bowf

M440 is a detongued X440. In short, a lot of folks were cutting the tongues off the X440 to get more RPMs out of it...so octura made a prop that had this already done to it.

The prop in the first picture looks detongued...but it might just be the angle.

Sean

Oh Yeah!!

Tongue?.... are you talking about the very front part of the blade that starts at the hub?

moparbarn

yes, the tongue is where you think. i still like tongue cut x-440's over the m-440. i know they're supposed to be the same, besides the tongue, but a tongue cut 440 has always been better/faster for me on my k&b 3.5 powered tunnels. if you feel it's still not "turning up" enough, round the tips down to 38 to 38.5 mm, as opposed to 40 mm stock diameter. props are cheap, don't be scared to try stuff.

Oh Yeah!!

COOL.......

I've installed the Octura X440 on my outboard prop shaft. I'm just a little concerned about the clearance between the prop and water pickup tube.

Is this alright?? (see pic)



Thanks,
Phil

moparbarn

since the prop pushes foward, it should stay clear, if it doesn't hit now. it is a tight fit, though. reducing the diameter, as i mentioned earlier, helps some.

topfuel4430

reduce the diameter some as Mopar suggested. Also, you are going to want to work that prop, they are not intended to be run out of the bag. They all need a fair amount of work for them to perform properly.

~JAMES

ob nut

My Feedback: (1)

First off, cut some of the water pick up tube.. Don't need so much hanging down. Leave about 3/16" - 1/4" sticking below the cav plate. Make sure the same angle is used when the cut is done. With the tube cut properly, the prop should clear it without issues.

Another prop not mention would be a 1440 that has been back cut..

jetpack

My Feedback: (1)

If you would like to do away with the water pickup tube it would be a simple conversion and still would work very well for you.

You would have to un-install the tube in the lower unit. It takes unscrewing the four power take-off screws and lifting the engine assembly off, and then five screws that hold the two lower unit halves together. Backing out the prop stub shaft assembly is a good idea to do first.

Dubro makes nylon landing gear straps (I think 4 pcs per package) that are inexpensive and can be used to hold a piece of brass tubing cut with the angle right on the back of your outside sponson, and just run a piece of fuel tubing from that to your motor.

I'll see if I can find the Dubro stuff at Tower Hobbies and post the link.

I'm having the same problem as you are with the clearance with my SS which is air-cooled that I am converting over to water cooled.

Here's the link to the straps at Tower. The stock pickup tube diameter is 1/8" brass. I suppose if you wish you could even go larger, because Dubro makes these in 5/32" also.

[link]http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD840&P=ML[/link]

You might have to add just a small mounting pad to the rear of the sponson just to give clearance for the wall thickness of the tubing, because this will mount things flush, and it will sit crooked if you dont leave room for the tubing to slip on.

I was kind of bummed out to discover this when I bent up my tubing and found that the hole on the cavitation plate was too close to the prop because I really like the idea of the motor getting water pumped to it from the prop, and not just at speed.

Mark mentioned leaving just a 1/4" or 3/16" cut past the plate, but I'm not sure this is going to cure it for you (I looked at my biggest prop too and it hits right at the top), plus I would also leave the tips alone on the prop. Shouldn't have to sacrifice any of the prop for just the sake of getting water to the motor.

Another thing I wonder about with the stock K&B tube is it is at the top of the cavitation plate, which on my boat when properly set up and running, never even comes close to being submerged. My propshaft is right at the waterline even with my sponson bottoms. It must get pumped with propwash, and not direct flow.

You're going to like a larger prop if the power is still up in your motor. The larger props like the engine to sit way higher and really free's up the RPM's and they start to wind-out really nice, and most likey you'll see a big improvement in top speed.

Oh Yeah!!

Cool!!!!!

Thanks!!!!!!!!!