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Go Back   SailNet Community > On Board > Gear & Maintenance > Prop Shaft Coupling
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Thread: Prop Shaft Coupling Reply to Thread
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Topic Review (Newest First)
04-29-2013 04:18 PM
casey1999
Re: Prop Shaft Coupling

Quote:
Originally Posted by katsailor View Post
Did you check you engine alignment?
When I removed all the coupling bolts, I checked allignment. It was good. I know the cutlass bearing is worn and I will replace that in the near future at haul out, along with all engine mounts, then do complete allingnment.
04-29-2013 04:06 PM
katsailor
Re: Prop Shaft Coupling

Did you check you engine alignment?
04-29-2013 04:04 PM
katsailor
Re: Prop Shaft Coupling

Coupling fit information

An interference fit coupling is the best and also the hardest to remove and install. The coupling bore is sized .001-.002 per inch of shaft diameter smaller than the shaft. For instance if you have a one inch shaft you will turn the end of the shaft to make sure it is perfectly round then bore the coupling shaft diameter - .0015 in. The key way and key on both the coupling and shaft is fitted before the coupling is heated and installed on the shaft. After it cools you are good to go and do not need a setscrew. You need a coupling puller to remove a interference fit coupling.

An sliding fit coupling is bored slightly larger than the shaft +.001 -.002/inch of shaft diameter. Dimple the shaft using a drill bit and install a setscrew in each hole, there should be one hole directly above the key way and one 90 degrees from the key way. Install a second setscrew to keep the inside one from backing out. Do not use a bolt, if a line or something gets near the spinning couple it will make you life very interesting very quickly.

Split couplings are easy to install however split couplings also fail usually at the most inopportune time, they were outlawed in the hoisting industry for anything that supports a load a long time ago.
04-29-2013 03:49 PM
casey1999
Re: Prop Shaft Coupling

Quote:
Originally Posted by CalebD View Post
Yep, our old bronze shaft had a gouge worn into it right at the stuffing box, which is why we decided to replace it.
Bronze is fairly soft as metals go.

Best practices say to wire up the set screw and couplings; so vibration does not allow it to back out.

Good work.
Hard to see in pic, but I did wire tie the set screw (it came with a hole in head for the purpose). I did not wire tie the coupling bolts- I am sure good practice but I would have a hard time drilling the Grade 8 bolts. The coupling is super easy to get to, so can keep an eye on it and check before each use.
04-29-2013 03:43 PM
CalebD
Re: Prop Shaft Coupling

Yep, our old bronze shaft had a gouge worn into it right at the stuffing box, which is why we decided to replace it.
Bronze is fairly soft as metals go.

Best practices say to wire up the set screw and couplings; so vibration does not allow it to back out.

Good work.
04-29-2013 03:04 PM
casey1999
Re: Prop Shaft Coupling

All the work went well. Hardest part was getting the correct bolt type and length. I used gear puller to gently push the shaft back, estimate only took about 20 lbs of force. The set screw was never installed so I drilled dimple and install new. The 4 bolts holding the coupling to the transmission output flange were little more than finger tight- lucky they did not break off during running. These 4 bolts were also 316 ss and coarse thread. I have read where not to use stainless for these bolts as they are not very strong, and can fatigue easily. Repalced the 4 stainless bolts with grade 8.

The other good thing that came out of this work is my shaft packing began to drip like normal. A few months ago the shaft packing had almost no drip. Could not figure out why it would stop dripping- that must have been at the time the shaft shifted the 3/4 inch and probably a small groove worn in the shaft at the shaft packing. When shaft shifted the groove was no longer at the packing- and it was very tight with larger diameter shaft. Plan to install new prop shaft at next haul out. The existing shaft is bronze- was extremely easy to drill the dimple for set (grog) screw.
04-25-2013 03:15 PM
casey1999
Re: Prop Shaft Coupling

Quote:
Originally Posted by CalebD View Post
Casey,

The set screw must go into a dimple on the shaft, so yes, you will have to drill one if there is none. Screw pressure on the shaft alone will not do it.

Of course I never knew there was a marina in Haleiwa having only once visited Oahu. Naturally I thought you'd be in the big harbor in Honolulu. Your spot looks pretty idyllic but without a lot of the industrialized amenities of Hono.
From my limited google research there are probably about 10 places in the city that could do your prop/shaft work. I was just looking for a place that seemed to specialize only in props & shafts. Most of the other places I found seemed to be multi-service boat places.
I suppose you live up near the North Shore also? You lucky dog!
Had a few minutes last night to look at the coupling. The two clamping bolts were only torqued to a few foot pounds- basically nothing. The clamp bolts do have lock washers but must have losened up over time. I tried to push shaft back by hand, but could not. I have a tool I will use tonight to try to push back the 3/4 inch (gear puller that can be used to push shaft without damage to trans or couplings). Should not be hard as I can see oily slide marks on the shaft where the shaft slid. Plan to replace the clamping bolts. The set srew I got was right size- 3/8 inch american thread- will drill a dimple and install.

If you ever make it to Hawaii again, let me know. We can take her out. I live a mile up the hill from Waimea bay, right in the sunset beach area. Not much marine service in Haleiwa- most down in Honolulu- about an hour drive- but on the otherside of island- so a 12 hour cruise by boat under good conditions.
04-24-2013 11:03 PM
CalebD
Re: Prop Shaft Coupling

Casey,

The set screw must go into a dimple on the shaft, so yes, you will have to drill one if there is none. Screw pressure on the shaft alone will not do it.

Of course I never knew there was a marina in Haleiwa having only once visited Oahu. Naturally I thought you'd be in the big harbor in Honolulu. Your spot looks pretty idyllic but without a lot of the industrialized amenities of Hono.
From my limited google research there are probably about 10 places in the city that could do your prop/shaft work. I was just looking for a place that seemed to specialize only in props & shafts. Most of the other places I found seemed to be multi-service boat places.
I suppose you live up near the North Shore also? You lucky dog!
04-24-2013 10:06 PM
casey1999
Re: Prop Shaft Coupling

Quote:
Originally Posted by CalebD View Post
I have a solid coupling (not split) and yes, there is a set screw which has to be wired so it does not decide to pull out. So my shaft is held in place at the coupling by the press fit and the set screw.
The key/keyway is on the prop end of my shaft.

See if you can torque down the split sides together. It may work.

Obviously I've never used this shop:

Marine Propellers Hawaii
(808) 537-6772
1100 Bishop St, Honolulu, HI 96813


but it would seem near the Alu Wai and perhaps convenient.

My boat is actually kept on North Shore Haleiwa. That is why haul out is such a problem. I can pay to have someone pull it out with a trailer at the harbor with a cost of well over $1,000. Or sail 60 miles off shore each way to a marine center that charges $400 for haul out and $70/day on the hard.

I will check out Marine props and see if they can check balance on my prop when I do haul out. I also would like to see prop is correct for the boat (over proped)? I had not Seen Marine Propeller advertised in the local boat mags, just gave them a call, they have a shop and can work props and shafts.
Thanks
04-24-2013 09:55 PM
casey1999
Re: Prop Shaft Coupling

Quote:
Originally Posted by Maine Sail View Post
A split coupling is held in place by the clamping action and a proper "fit". Good ones will also have a set screw which should always be "spotted" or dimpled into the shaft.

With split couplings it is very important to tighten the clamping bolts evenly, like lug nuts, or you can create an alignment issue. Contrary to popular misconceptions about "splits" they still require a fit & face when installed.
I picked up some different size set screws (look more like squaure head bolts) at hard ware store. Will see how they fit. All the ones I got are american thread (not metric as they did not have). I was told the set screws are normally american threads. From what I see on Yanmar parts manual, the yanmar coupling does not have set screws. Maybe mine is a after market coupling. Plan to loosen all the bolts. Slide prop shaft to its proper location. Tighten up the clamp bolts and install the two set screws. If she runs good, will run that way to November or so, then hual out and go through the entire drive train.

When you say spot or dippled to the shaft, does that mean I should drill a dimple into the shaft prior to installing set screw, or just torque down on the set screw to "set" it into the shaft?

Regards
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