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k and b outboard

Old 06-10-2003, 04:53 PM
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gmeister
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Default k and b outboard

I have a K and B 3.5(.21) on a Dumas hot shot. I have broke 3 flex shafts, all within the first 4 runs of each new flex shaft. What am I doing wrong.
Should I not drop the boat in the water?
Prop to big?(Came with the prop)

Any help??

Gary
Old 06-21-2003, 12:01 AM
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toonces
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Default k and b outboard

A noligable boater that i know said that when the prop cavitates then suddenley gets a solid bite the flex saft may break, I think if you are launching at a high throtle setting than mabie it twists when it hits the water?
Old 08-08-2003, 01:12 AM
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Mike Ferretti
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Default k and b outboard

Try giving it a good throw each time you launch it. The Flex cable must be kept well GREASED at all times!!!! If the cable housing sleeve is worn replace it. Maybe you got a batch of defective flex shafts...... GREASE the *&^%$#^* out of EVERYTHING in the lower unit!!!! If the fex shafts look like they have any defects they probably do. The whole Flex shaft should look nice, and neatly, and tighly wound. If you see any spots on it that don't look like that, it's defective, or it's starting to come undone from the time you have put on it already............Also make sure the engine is running in the correct direction BEFORE you put in the water!!! If you put your hand down by the prop, ( NOT TOO CLOSE!! ), you should feel some air coming from it. If you don't feel any air, the engine is running backwards. The flexshafts are only designed to transmit torque in the forward direction. The leads on your starter motor may have to be connected to the field battery backwards from what seems normal, to make this correct dierction of rotation happen. Also you may try raising the engine out the water more. The prop may be to deep in the water. Only the bottom half of the prop is supposed to be in the water when your boats is up on step at full speed. I,d reccomend octura X438, X440, or X442 props as a starting point. Do NOT use a plastic prop!!!!, even if thats what it came with! They do NOT work on gas motors!
Old 08-08-2003, 11:30 AM
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gmeister
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Default K and B 21

Thanks everyone for all of the info. I have taken the advice of many and greased the lower end with white lithium grease.
I have 4 or 5 runs on it and everything seems good.

Just a thought. When this thing breaks, the boat is running wide open down the straight away, not when I launch.
Old 08-10-2003, 01:47 AM
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Mike Ferretti
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Default k and b outboard

I don't know what to tell you... I think maybe your experiencing what is actually NORMAL now. One flex shaft should last you at least one FULL day of running your boat or even racing. I actually run only the 7.5's, so Ron O., or one of the other guys would be in the know better.... Breaking flex shafts is just a fact of life in the big city...... If you like to go run your boats, or racing for that matter, without being shut down, you need to keep at least one spare on hand at all times, especially if your racing! Anytime you find anybody that has them I wouldn't mess around with buying just one or two, I'd reccomend buying them SIX at a time. Especially if you run your boats a lot, which I gather that you do from this thread...Parts for these Outboards can be hard to find so when you do find them it's like gold.. Do you get my drift?
Old 08-11-2003, 09:44 PM
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rcnut1
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Default k and b outboard

I dont know what you guys are doing but i have made five years on two flix drives in the same engine. If thay are brakeing them that fast you need to talk to K&B and find out if there is something you are doing wrong. Are maybe something wrong with the flix drives.
Old 08-23-2003, 11:12 PM
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Safe_Cracker
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Default Also...

Don't forget there is supposed to be a small gap down by the prop to allow expansion from cable twist. If there is not a gap then the cable will snap and quick!
Old 08-24-2003, 03:14 AM
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Ron Olson
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Default k and b outboard

You are having an unusual amount of breakage. I've only had one break on my 3.5 tunnel and oddly enough, a friend was at the same race and broke one also that day. It's a good thing that I had 2 spares. I have replaced them when they do look like they are getting in bad shape.
I have always given all of my boats a flat level toss into the water. Number one reason is for less shock to the driveline and #2, they'll have less of a tendency to flip over backwards, not a good thing to do at a race.
Watch the RPM's so that it is not too high, flipping is one sure sign that of that.
You won't be able to get an X442 under the cavitation plate unless it is cut down. I ran mostly X437's and X438's on mine.
At what end are they breaking at? Tear it down to look for wear there that might be breaking the cables.

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