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Old 10-03-2016, 09:32   #1
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Transmission to Prop shaft

Greeting My Fellow Sailor's I have a problem that with the Vast Knowledge on this site I have learned a whole lot. Your Guidance and Help with this will be Greatly appreciated So Here is my problem I have a 1inch shaft on the prop end and it has a 3 bolt pattern with a 3inch between bolts and the Transmission has a flex flange that is a 4 bolt pattern with 3inch between bolts
Every thing else is all good what do I need to do that will make the most sense replace the shaft flange or replace the flex coupler with a 3 bolt flange I am tight on cash due to the cost of installing the engine the haul out and the dry pad for the work to be done on I would welcome any and all Idea's on what step I should do with the least amount of cost involved also least amount of labor I surely welcome any Answers
Thank You SV UsCa Jack
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Old 10-03-2016, 09:35   #2
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Re: Transmission to Prop shaft

3 bolt is a bit unusual, get a 4 bolt coupler that matches your engine/coupler flange.
BTW, do not use nylok nuts on the bolts. Use conventional lock washers and good quality, higher grade than basic bolts and nuts.
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Old 10-03-2016, 09:40   #3
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Re: Transmission to Prop shaft

Thank you so I should pull the shaft and replace the Shaft flange and make sure I use grade 8 bolts
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Old 10-03-2016, 09:49   #4
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Re: Transmission to Prop shaft

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Originally Posted by Cheechako View Post
3 bolt is a bit unusual, get a 4 bolt coupler that matches your engine/coupler flange.
BTW, do not use nylok nuts on the bolts. Use conventional lock washers and good quality, higher grade than basic bolts and nuts.
Why not Nyloks ?

Just bought an R&D shaft saver type coupling and it came with Nyloks.

I understand that they are one time use in a critical application like this, but is there a technical reason not to use them ?

Cheers,
JM.
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Old 10-03-2016, 09:50   #5
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Re: Transmission to Prop shaft

You have to pull the flange to remove the shaft anyway... so no need to remove the shaft... just the flange with a puller.
As long as you have it off though, slide the shaft back and look at the surface of the shaft where it resides in the packing/cutlass bearing... they are often corroded from sitting with stagnant moisture in there, and tend to tear up the packing that way.
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Old 10-03-2016, 09:57   #6
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Re: Transmission to Prop shaft

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Originally Posted by NahanniV View Post
Why not Nyloks ?

Just bought an R&D shaft saver type coupling and it came with Nyloks.

I understand that they are one time use in a critical application like this, but is there a technical reason not to use them ?

Cheers,
JM.
So…. While on the hard in Trinidad, I decided to clean up the rusty coupling, repack the stuffing box, realaign the engine etc. Got it all done and decided on new bolts and Nyloks. It was all properly tight and secure. After less than 8 hours of use I heard this loud rattling while motoring. One of the 4 bolts was completely gone. The other 3 were almost off, the holes in the coupling were damaged etc. Proceed accordingly! Your choice. My theory is the heat of the engine application softens the nylon.
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Old 10-03-2016, 10:09   #7
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Re: Transmission to Prop shaft

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So…. While on the hard in Trinidad, I decided to clean up the rusty coupling, repack the stuffing box, realaign the engine etc. Got it all done and decided on new bolts and Nyloks. It was all properly tight and secure. After less than 8 hours of use I heard this loud rattling while motoring. One of the 4 bolts was completely gone. The other 3 were almost off, the holes in the coupling were damaged etc. Proceed accordingly! Your choice. My theory is the heat of the engine application softens the nylon.
OK, you had a bad experience with nyloks, but, spring washers from questionable sources can be bad as well. I don't think your experience should mean never to use nylocks.

Perhaps a better take-away from your experience would be to monitor newly installed equipment in the first few minutes of operation then after a few hours, then days, then yearly.

Cheers,
JM.
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Old 10-03-2016, 10:19   #8
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Re: Transmission to Prop shaft

Yeah, I hear you. But sometimes I've found "if it aint broke, don't fix it!" is a great policy!
Still, the heat thing makes me nervous, but I think some people have used them successfully.
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Old 10-03-2016, 10:50   #9
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Re: Transmission to Prop shaft

I've never had any problems with Nyloks backing off. I use them on many different applications. I too recommend that you change the shaft flange, to 4 bolt unit; that is the standard of the industry.
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Old 11-03-2016, 08:36   #10
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Re: Transmission to Prop shaft

I bought new grade 8 bolts for my shaft flange and the local fastener store recommended an all steel locknut. No nylon insert. Sorry but I don't recall the name or brand but they're out there.
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Old 11-03-2016, 09:23   #11
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Re: Transmission to Prop shaft

The 4 Shaft coupling bolts on my Ranger 33 are lockwired together to prevent loosening. Small engines with few cylinders put out a nasty cyclic rotary vibration which can readily loosen nuts and bolts. 316 stainless bolts and nuts with lockwire holes are available from McMaster-Carr at good prices
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Old 11-03-2016, 10:28   #12
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Re: Transmission to Prop shaft

Quote:
Originally Posted by Chevy1217 View Post
Greeting My Fellow Sailor's I have a problem that with the Vast Knowledge on this site I have learned a whole lot. Your Guidance and Help with this will be Greatly appreciated So Here is my problem I have a 1inch shaft on the prop end and it has a 3 bolt pattern with a 3inch between bolts and the Transmission has a flex flange that is a 4 bolt pattern with 3inch between bolts
Every thing else is all good what do I need to do that will make the most sense replace the shaft flange or replace the flex coupler with a 3 bolt flange I am tight on cash due to the cost of installing the engine the haul out and the dry pad for the work to be done on I would welcome any and all Idea's on what step I should do with the least amount of cost involved also least amount of labor I surely welcome any Answers
Thank You SV UsCa Jack
You might ask a machine shop. Even a rough sketch will probably give them an idea and let you know what to bring them and probably the cost. Pic might help but go with a sketch that has measurements.
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Old 11-03-2016, 10:50   #13
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Re: Transmission to Prop shaft

Nylon nuts can have a heat problem with the nylon insert melting. Correct use is dependent on location and temperature of heat. Use distorted thread all metal locknuts. Been used in aviation and race cars for years. Strength and metal rated for applications. Most good nut and bolt suppliers will have them in stock,
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Old 11-03-2016, 11:03   #14
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Re: Transmission to Prop shaft

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You might ask a machine shop. Even a rough sketch will probably give them an idea and let you know what to bring them and probably the cost. Pic might help but go with a sketch that has measurements.
Quoting myself!

PS, replacing the shaft flange will be cheaper than the flex..
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Old 11-03-2016, 11:04   #15
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Re: Transmission to Prop shaft

Castellated nut and a cotter pin is the standard for aircraft on parts that are subject to rotation, but I think most boats out there have regular nuts and spit lock washers.
I won't use self locking nuts on SS fasteners though, SS galls so bad that without anti-seize they often seize, and if your anti-seizing self locking fasteners, it seems to defeat the point?
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