K&B lower

[mike stover]

This one has me baffled!

K&B lower, rossi powerhead, x637 prop (sharpened and ballanced), silver bullet pipe, 50% nitro.

No mater what i have tried it keeps breaking flex shafts. It breaks a shaft every day that i run it.

I have tried swapping the teflon liner for brass. I was greasing the shaft, so i switched to oiling the shaft every fill up on fuel.

This is getting very agrivating, and expensive.

The flex fit seems good, no binding.

It usually makes it through about 3-5 tanks of fuel then breaks.

I am totally lost!!!!!!!!!!!!!!!!!!!!!!!!!!!

Any ideas?????

Mike

 

[julianconde]

buy a Lawless lower Unit problem solves my friend his name is fred

(607) 687-0143 [email protected]

 

[Terry Flynn]

I had a few break on me also, novarossi with a K&B lower. I found out the shafts were a little too long. Pull the power head and put in a new shaft then set the power head back on it should fit flat. Mine had a gap when I tried this. I had 6 shafts and they were all different lengths. Since I ground them all to fit I haven’t broke one shaft.

Hope this helps.

Terry

 

[jetpack]

Dremel grind the very ends of the square corner round on the swage, very small amounts at a time, do not cut through and do not burn the strands.

The shaft cannot have ANY clicking when tried by hand when assembled without the powerhead.

The flex shaft does not feed straight into the square holes and lobes around and causes too much shock to the bundle.

It helped stop the same problem with mine.

Try stopping and inspecting the flex before it breaks and look for where the wear spots are on the ends and slightly dress them.

You can also use layout dye or magic marker to help spot in the shaft.

The whole problem I found out all lies in how the very tips of the corners of the swage ride in the socket.

 

[HTV Boats]

I agree with the concensus here your shaft is probably binding. The cable has to have the ability to float just a bit between the two square sockets in the prop shaft and PTO. Binding even a little will rob HP especially if your binding enough to break shafts.

One other way to clearance is to make some 1/16th & 1/8 inch spacer plates between the lower and powerhead. Metal or composite just a center hole and the 4 bolt pattern are easy with a drill. Composites can also prevent some heat loss into the lower.

Mic

 

[moparbarn]

where are they breaking? if they are breaking at the bottom end, where the cable leaves the liner, there is a good chance that the lower is bad. i ran into this issue this season, when i swapped lower units on my cmb greenhead/k&b combo. tried stainless, brass & nylon liners, k&b, hyperformance & nitro watersports propshafts, k&b, kris flynn & lawless shafts. all made no differance. it would break a flex in anywhere from 1 or 2 tanks to as little as 5 feet from launch. i'm guessing the channel for the liner in the lower & the propshaft threads weren't lined up ........try swapping lower units & see if it helps.

 

[Kevin Knapp]

I’m pretty new to this but one of the first things I was told was to shave down the cable by about a 1/8in so there was no binding. I’m to understand that the cables stretch a bit over time, especially when they are new. That’s just what a few other boaters told me.

 

[SayMikey]

i had a bad stub shaft causing a problem. Went thru several shafts replaced the stub and problem solved. I think over time the square tapered and it started ripping the lower end off