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Author Topic: Two prop shafts?  (Read 2740 times)

fred12

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Two prop shafts?
« on: August 25, 2017, 11:40:20 am »

A simple question to all you seasoned boat builders but to me not so simple
i have just installed two prop shafts in my boat and on the propeller end is nuts do i leave them on or take them off sorry for the stupid question
regards.
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Colin Bishop

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Re: Two prop shafts?
« Reply #1 on: August 25, 2017, 12:07:58 pm »

The nuts are there to lock the propellers when you have screwed them pn to the shafts. This stops them unscrewing and falling off when the shafts rotate. You should also fit a washer between the nut and then end of the prop tube as this helps prevent water finding its way up the tube and into the boat.

Ideally you should also have some sort of collet fitted to the inboard end of the shaft to restrict it moving outwards and placing a strain on the motor coupling and motor bearings. It's all pretty straightforward really.

Colin
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TailUK

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Re: Two prop shafts?
« Reply #2 on: August 25, 2017, 02:25:56 pm »

Between the collet or another nut on the inside end and the nut and washer on the outboard end you can adjust the "end float" of the shaft.  Too tight and there's undue strain on the motor and too loose you'll get vibrations and wear on the motor coupling.  I tighten one or both of the nuts until the shaft binds and then back one nut off a little until the shaft rotates freely.  The tube should have some kind of packing in it to keep it water tight.  Some recommend oil via a feed tube or grease packing before putting the shaft in.
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fred12

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Re: Two prop shafts?
« Reply #3 on: August 25, 2017, 02:41:57 pm »

thanks lads
regards fred
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CGAux26

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Re: Two prop shafts?
« Reply #4 on: August 25, 2017, 04:15:44 pm »

Nylon washers are best as they are soft and won't wear the ends of your stuffing tubes.


The end float Colin mentions needs to be less than 1/32".  Just enough you can feel the shaft move back and forth after all adjustments are complete.  Come by my house tomorrow and watch me install the drive train in my new CG-36500 model.   %)
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fred12

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Re: Two prop shafts?
« Reply #5 on: August 25, 2017, 06:11:44 pm »

Hi, I don't think Texas is close to Spain or I would pop over
regards fred
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CGAux26

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Re: Two prop shafts?
« Reply #6 on: August 25, 2017, 06:50:10 pm »

Fred, if you get here Saturday or Sunday you can "enjoy" this big hurricane that's bearing down on Texas with us.
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fred12

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Re: Two prop shafts?
« Reply #7 on: August 25, 2017, 06:57:37 pm »

whatever floats your boat. KEEP SAFE
regards fred
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merseyferry

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Re: Two prop shafts?
« Reply #8 on: August 25, 2017, 07:08:26 pm »

fred,dont forget to grease the  shafts :-))
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fred12

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Re: Two prop shafts?
« Reply #9 on: August 25, 2017, 09:11:32 pm »

will do many thanks
regards fred
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fred12

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Re: Two prop shafts?
« Reply #10 on: August 26, 2017, 07:50:07 am »

CGAuc26    Just been watching the report on Texas hope you are safe and well.
regards fred 
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Brian60

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Re: Two prop shafts?
« Reply #11 on: August 26, 2017, 09:18:25 am »

whereabouts in spain fred?

fred12

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Re: Two prop shafts?
« Reply #12 on: August 26, 2017, 09:54:49 am »

Hi Brian 15mins from Torrevieja 40 mins from Alicante that is south of Alicante.


regards fred
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CGAux26

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Re: Two prop shafts?
« Reply #13 on: August 26, 2017, 02:26:28 pm »

It's Saturday morning here and we are safe and dry so far.  The hurricane is ashore north of Corpus Christi, 200 miles southwest of us.  But mucho rain and a little wind for us now.


Thanks for your concern.
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pdq

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Re: Two prop shafts?
« Reply #14 on: August 28, 2017, 08:18:46 am »

In relation to the OP, if you are fitting two propellers does one have to counter rotate against the other or would you fit them rotating the same way? Thanks for any responses. Paul
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malcolmfrary

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Re: Two prop shafts?
« Reply #15 on: August 28, 2017, 08:42:38 am »

In relation to the OP, if you are fitting two propellers does one have to counter rotate against the other or would you fit them rotating the same way? Thanks for any responses. Paul
Depends on the boat in question, and what you prefer.  There has been a lot of discussion about which way counter rotation should happen if that is chosen, a a quick shot with the search on site will show.
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pdq

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Re: Two prop shafts?
« Reply #16 on: August 28, 2017, 11:32:29 pm »

Ok thanks Malcolm, I will take a look. Paul
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CGAux26

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Re: Two prop shafts?
« Reply #17 on: August 29, 2017, 12:19:58 am »

Without going into the whole lecture (which you can find with a search of this website) props need to be counter rotating to offset prop walk, primarily when going astern.  It you use independent throttles the counter rotating props can help in pivoting the boat on its beam ends, too.
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