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Thread: Propeller strut sealing

  1. #1
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    Default Propeller strut sealing

    Hello,

    I noticed a couple of my boats with propeller struts seem to loose the grease after 1 or 2 times running. After you grease the shaft the open hole is still exposed to water and air. It seems like the grease comes out as fast as it goes in sometimes. I'm not sure why the manufacturers don't supply a plug for this. Anyway I found a small screw that would thread into the hole. I then tightened it until I felt it bottom out against the shaft. Then I backed it off about a half turn and sealed it with liquid electrical tape. No more grease comes out that hole Any opinions appreciated. Howard

    IMG_3041.JPGIMG_3043.JPG

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    so can you unthread the screw to refill?

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    No problem, You can unscrew and re-grease as many times as you want. The liquid tape just seals it and stops the screw from backing out.

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    that's awesome!

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    Quote Originally Posted by Howard View Post
    Hello,

    I noticed a couple of my boats with propeller struts seem to loose the grease after 1 or 2 times running. After you grease the shaft the open hole is still exposed to water and air. It seems like the grease comes out as fast as it goes in sometimes. I'm not sure why the manufacturers don't supply a plug for this. Anyway I found a small screw that would thread into the hole. I then tightened it until I felt it bottom out against the shaft. Then I backed it off about a half turn and sealed it with liquid electrical tape. No more grease comes out that hole Any opinions appreciated. Howard

    IMG_3041.JPGIMG_3043.JPG
    Hi,
    Do you run with no space at the prop dog and strut or stinger ?
    Last edited by lenny; 12-19-2011 at 12:09 PM.

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    Quote Originally Posted by Howard View Post
    Hello,

    I noticed a couple of my boats with propeller struts seem to loose the grease after 1 or 2 times running. After you grease the shaft the open hole is still exposed to water and air. It seems like the grease comes out as fast as it goes in sometimes. I'm not sure why the manufacturers don't supply a plug for this. Anyway I found a small screw that would thread into the hole. I then tightened it until I felt it bottom out against the shaft. Then I backed it off about a half turn and sealed it with liquid electrical tape. No more grease comes out that hole Any opinions appreciated. Howard

    IMG_3041.JPGIMG_3043.JPG
    There are several reasons for that hole you decided to plug up. First one,........as heat or friction occurs the grease is allowed to expand and push out thru the paths of least resistance. Thats normal. Grease (oil suspended in a gelatanous media) is what provides lubrication. Blocking its exit path does not make a better lubrication system. Water and grease will mix. Its an accepted part of driveline operation.
    Second one,.....You should be taking your flex assy apart after every run. Then clean and regrease. Not on the second or third. Its part of a maintenance plan you should adhere to and ensure happens every time. Other wise you will break drive lines due to mechanical failures. Lose a couple $30 or $50 props and it will become engrained. Comes with experience.

    John
    Change is the one Constant

  7. #7
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    Well I quess everyone has an opinion but I believe your statement is totally inaccurate. First off we are not talking about the flex shaft. I agree the flex shaft should be greased often. I was talking about the strut that holds the drive dog/prop shaft. The hole on the side is for filling. When you close it off as I did the grease will now only escape through the ends. This is where the bushings are, thus it will grease the bushings as it escapes. If it goes out the open hole on the side (as you mentioned) what good is the grease other then a waste.


    Howard

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    Quote Originally Posted by Howard View Post
    Well I quess everyone has an opinion but I believe your statement is totally inaccurate. First off we are not talking about the flex shaft. I agree the flex shaft should be greased often. I was talking about the strut that holds the drive dog/prop shaft. The hole on the side is for filling. When you close it off as I did the grease will now only escape through the ends. This is where the bushings are, thus it will grease the bushings as it escapes. If it goes out the open hole on the side (as you mentioned) what good is the grease other then a waste.


    Howard
    Totally is a little harsh, when the flex is loaded and binds up it will push any lubricant to its least path of resistance.. as quoted.. Gravity will take care of said grease when not used?? Hence drive shaft??


    You always leave a gap for flex, even bigger for gas saw rig's..."some almost 10mm metric"..

    Better to be safe than sorry?? How much is grease compaired to driveline components? Kind of speaks for itself..

    How long does it take to pull down and re lubricate compaired to re ordering parts and watching others have fun...inmho

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    Sorry if I was a little harsh, but again this thread I started has Nothing to do with the flex shaft

    Please read my first post. Maybe you don't or not familiar with this setup. Not all boats have a propeller strut that holds the dog bone. This is the part after the flex shaft.



    Howard

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    These setups are mostly used in Proboats. As I mentioned most boats don't use a dog bone (as it's called) this is a short shaft that goes inside the strut and is a solid shaft about an inch or so long. It rides on two bushings. Just wanted to clarify what this thread is about.

    Howard

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    [QUOTE=Howard;377909]Sorry if I was a little harsh, but again this thread I started has Nothing to do with the flex shaft

    Please read my first post. Maybe you don't or not familiar with this setup. Not all boats have a propeller strut that holds the dog bone. This is the part after the flex shaft.



    Very familiar,not many boats have a strut that holds the bone.. And i did read your thread before responding.. No disrespect intended.. Massive rpm, limited room/space, high viscosity... kinda needs room to breath so to speak... Not talking about a ford 9inch are we... All good, do what makes you happy... personally i'd spend the extra 2mins cleaning up and a couple of dollars re lubing just in case .. each to there own cheers

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    Quote Originally Posted by TINY View Post
    You always leave a gap for flex, even bigger for gas saw rig's..."some almost 10mm metric"..
    No, you're wrong in this case.
    Howard, I think you already know this, but you shouldn't be running a gap between your drivedog and stinger. As long as it's not causing drag or compressing that little washer you are fine. Running a gap will only cause problems with this style setup.

    Ideally you could weld that hole shut, finish it smooth, and put a grease fitting on the TOP of the stinger, so it's not in the water causing drag and turbulating water before it hits the prop.

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    BTW- People love to hate on things that get posted in this section so don't be surprised if your ideas get critiqued. You know what works for you and what doesn't and you can take the feedback you get and evaluate what is right/wrong. Thanks for sharing it with us.

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    Please don't get me wrong but do you realize how much the flex shortens on high load??? A thrust washer will bind and you will blow your esc in seconds.... Unless of course your running small props low pitch on low rpm.. Eg zero or no load... Go see the back of a saw boat.. You'll understand.

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    I'm guessing the flex cable on Howards set-up is a square drive and "floats" in the prop shaft requiring 0 gap between the drive dog and the strut itself, No?

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    Correct osprey21 :-)

    I'm not even sure what those guys are talking about. I just wanted to share my idea about a proboat I have. I wasn't asking for an explanation of everyone's theories about qua-tom physics And I wasn't saying NOT to grease the shaft often. I WAS JUST SHOWING A WAY TO MAKE A FILLER PLUG to unscrew and keep the grease in. I don't know of any boat, airplane or car with a rear, transmission or engine that has an open hole anywhere that will allow fluid out.

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    Thanks for the heads up that its a square drive setup,

    Now it makes sense to me,lol

    But yes, Rears, Transmissions , Engines, Have vents in them to relieve pressure or they blow seals out.

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    Quote Originally Posted by TINY View Post
    Please don't get me wrong but do you realize how much the flex shortens on high load??? A thrust washer will bind and you will blow your esc in seconds.... Unless of course your running small props low pitch on low rpm.. Eg zero or no load... Go see the back of a saw boat.. You'll understand.
    I have some pretty fast boats tiny, so I don't really need to look at anyone else's. I understand what you're saying but I think you're just not familiar with the setup on Howard's boat. The flex is allowed to shorten without binding the drive dog against the back of the stinger/strut.

  19. #19
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    I had a square drive on an older nitro boat and the flex just floated in the collet to allow for contraction.
    It was supposed to be easier on the engine bearings because the stress is at the strut.
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  20. #20
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    A square drive or full floating flex does not require spacing between the drivedog and the strut, just needs a washer, but a full length flex with stubshaft does require a spacing.

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    Is there a cut off point for higher rpm set ups to require the strenght and trueness of a 1piece shaft from a floating square drive flex? And does a wire drive set up grow or shrink under high rpm, also requiring a drive dog to washer spacing?

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    No matter if you have a square drive or not the prop thrust will always push against the end of the stinger which just increasesrotational load on the motor. When you take the load at the motor...WITH a thrust bearing you are then reducing your load for the motor to rotate easier. I have never seen the benefit of a 2 piece unit like that...except they WILL round the shaft off eventually or may quickly depending on props in and out of the water. I have sold tons of new flexes that people said the square ends will not hold up. Also they are not easier to service. I also wwipe my wires or flexes down each run and grease them. Just something I do to makes sure that driveline is as good as can be for each run. Just my 2cents...worth about 1...LOL

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    You still leave the gap on wire...when you put the stuffing tube bend in rightplace (just the J up thru the hull) the push of the prop will actually give you clearance at the bend and gives you a much free-er (good word) running drive system.

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    Jeff, you being the wire master, how big should the gap on an 078 be? the wire is ~12 inches (oh yeah and the drive cable is also that long )

  25. #25
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    I respectfully disagree with both points u made. First the mixture of water/grease that develops actually breaks down the viscosity and thickness of the grease and it passes out harmlessly around the rear of the strut around the bearing/stub shaft fitting. No 2 I have run rc boats since 1978 and never once not once had a cable fail me. I DO NOT remove it after each run and re lube. Rather, i hand rub each cable using a drill mounted in my vise with the speed locked in and the flex cable on the business end. I grease up the shaft and with a greased rag, plug in the drill and run the rag up and down the shaft for about 1 minute. This works the grease deep into the flex shaft. I store them in ziplock bags greased. On run day I simply install them as is run them all afternoon, and NEVER have lost a flex shaft.

    Personally I like this idea of the thread and seal tip and plan to try it.





    Quote Originally Posted by m4a1usr View Post
    There are several reasons for that hole you decided to plug up. First one,........as heat or friction occurs the grease is allowed to expand and push out thru the paths of least resistance. Thats normal. Grease (oil suspended in a gelatanous media) is what provides lubrication. Blocking its exit path does not make a better lubrication system. Water and grease will mix. Its an accepted part of driveline operation.
    Second one,.....You should be taking your flex assy apart after every run. Then clean and regrease. Not on the second or third. Its part of a maintenance plan you should adhere to and ensure happens every time. Other wise you will break drive lines due to mechanical failures. Lose a couple $30 or $50 props and it will become engrained. Comes with experience.

    John

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