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Thread: Shaft Log: questions

  1. #1
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    Default Shaft Log: questions

    My plan was to use a two cutlass bearings-shaft log system, this will secure the 1 1/4 in SS shaft, both enternally embedded into deadwood. One at the stern post , the other attached/embedded into the frame floor. As it comes up at slight angle toward the end of shaft it would couple to a Lansdrop Gen 11 shaft seal. Lenght of shaft is short, @ 4 feet. My question is what to make the shaft log out of? They have a multitude of Duramax cutlass bearing with names like Doris and Della, these being 1 1/4 inch internal diameter for the shaft to go thru, but what type of material do you use for this bearing to insert into. Is PVC pipe a no -no, and why? The dead wood and floors are made of Long leaf pine, so I'm not really concerned with rot or sepage. Another problem I have is that my stern post is 3 inches thick, remember I made a mistake and under sized the stern post because I had this beutifull piece of old growth LL pine that fit perfectly during the build and I missed the correct thickness during build

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    Default Re: Shaft Log: questions

    Chuck, Buck Algonquin ( www.buckalgonquin.com ) will sell you a bearing housing and tube made out of bronze, with this shaft length, you don't really need, or want a forward bearing, Cheers, BT

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    Default Re: Shaft Log: questions

    A superior tube can be homemace with epoxy and FG. A resin tube is very strong and less metal to go "funny" down the road.A machine shop can turn the end to take the bearing.
    I am a bit confused about 2 cutlass bearings. An inside bearing would not be a cutlass. Cutlass is a wet bearing. Gonna use an aqua-drive?
    If your deadwood is too skinny and the shaft is only 4' long ,can you make the shaft 1"? ,cuz then you can make the tube thinner.

  4. #4
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    Default Re: Shaft Log: questions

    I am biulding John Gardner's Garvey out of plywood. I have used a cutlass bearing at the outboard end and a normal stern bearing at the inboard end. The stern tube has been embedded in the structure of the keel/skeg assembly. The stern tube is a copper pipe with a wall thickness of about 4/5 mil. The tube has a thread cut on both ends and the bearings screw onto these threads. Before epoxying them into place I made sure they were in alignment. This has given me an assembly that will not move at all and I believe, once I have used the right sealing rope in the stern bearing. will not leak at all. I sourced these parts from the company that provided my prop.

  5. #5
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    Default Re: Shaft Log: questions

    I am not sure what is meant by a normal stern bearing at the inboard end. Every normal shaft I've seen is supported only at the ends: out back by the cutless bearing and up front at the coupling. There are some boats with really really long shafts requiring some sort of pillow bearing in the middle but that's pretty rare.

    Are you perhaps, by inboard normal stern bearing meaning the stuffing box?

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    Default Re: Shaft Log: questions

    Not everyone can make a glass-epoxy composite tube to adequate quality.
    G10 glass-epoxy tube can be bought from McMaster and other plastic suppliers.
    PVC pipe is not strong or heat tolerant enough.

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    Default Re: Shaft Log: questions

    Chuck, While fiberglass tube can be done, the use and advantages of the conventional tube and bearing housing are hard to beat. Changing the cutlass bearing in a glass tube requires removing the shaft each time, depending on your situation, that may or may not be an issue. As to the metal problem, most boats I see range from 40 to 80 years old, and the shaft tube is almost never an issue...Cheers, BT

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    Default Re: Shaft Log: questions

    A cutlass bearing can last a LONG time if the engine is in alignment. That means, being aligned WITH the bearing. ( Unless one has a jumpy motor, like a Volvo MD1) By the time a chap needs to replace a cutlass, I would think one would want to pull the shaft, just to check it and re-new the coupling bolts.
    I cannot speak to a 40-80 YO copper or bronze tube.Except I would certainly re-new it,just for kicks and giggles!

  9. #9
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    Default Re: Shaft Log: questions

    The two-shaft bearing system is workable. Sometimes the second bearing is a second cutless bearing in the shaft tube, sometimes it's a carrier bearing located forward of the stuffing box. I've worked on boats that had as many as four carrier bearings. That was a 110' salmon tender with the engineroom right forward, and the shaft running under the fish hold.
    This approach works better in boats that are quite rigid. It doesn't work very well with a soft-mounted engine, because the shaft is quite rigid, while the engine is all over the place.
    For a wooden boat of moderate size, the approach I like is a single cutless bearing just forward of the propeller, a shaft tube running through the stern post and deadwood, an inside-mounted stuffing box that's mounted on a length of rubber hose, and a soft-mounted engine.
    I've installed many of the urethane "drivesaver" couplling buffers, but have come to the opinion that they're an added expense that doesn't do anything useful.
    In this system the engine can move around, the stuffing box goes with it, and the cutless bearing is far enough aft that it can accept the little bit of angular deflection that the engine mounts allow.
    One additional point that's quite important...
    If your boat currently has a four cylinder gasoline engine, like an Atomic Four, Palmer P-60, or Greymarine, it may have a hard mounted stuffing box. If you repower with a diesel, and if you soft-mount the diesel to cut down on vibration, you may have trouble with the old stuffing box. Simply put, the engine movement generates a lot of side-loading on the stuffing box, because it can't move around as the engine and shaft do. The problem most often appears as the stuffing box working loose, or breaking mounting bolts, or pulling the bolts out of the timbers, or wearing the packing nut into an eccentric shape.
    The solutions to this problem are to: A) hard-mount the engine. B) Switch the stuffing box to a soft-mounted type with a rubber hose.

  10. #10
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    Default Re: Shaft Log: questions

    RE: shaft tubes. High-strength plastic or FRP can work fine as a shaft tube, preventing leaking through checks in a wooden shaft log. One good thing is that they're cheaper than bronze, and because they are electrically inert, they won't interact with the wood. A good thing about bronze is that you can have the outboard end of the tube threaded, and then bore and tap the inside of the stern bearing, so that the two are very firmly joined with a water-tight thread joint. A good thing. Also, on the inboard side the shaft tube can be allowed to protrude a few inches, and then a piece of rubber hose clamped over that, and the stuffing box clamped to the inboard end of the hose.
    It is possible to retrofit a shaft tube into a boat that has always had a simple hole bored through the sternpost, deadwood, shaft log, etc. It requires using a couple of stuffing boxes as bearings fore and aft, a piece of old shafting set up with a cutter, and a very powerful drill motor. It works, but takes a long time. It's a good way to break your wrist, when the cutter snags a bolt in the deadwood, and the Milwaukee Hole Hawg quits spinning the cutter shaft, and instead spins you.
    All this is a good argument for offset shafts, which use a simple tube sticking through the hull planking, the tube welded to a plate that's been shaped to fit the inside of the planking. The stern bearing is usually mounted in a strut, although it's possible to bore out the tube so that a cutless bearing can be pushed into it. On the inboard end a rubber hose can be slid over the tube, with a stuffing box clamped on the forward end of the hose.
    This arrangement is pretty simple, and in many cases cheaper than the conventional arrangement.

  11. #11
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    Default Re: Shaft Log: questions

    The olde-timey solution to a checked and leaking shaft log is to dry out the crack (I use a wet-dry shop vac. Not exactly olde-timey...) and then pour hot tallow into the crack It runs into the crack until it hits cool water, where it congeals and hardens. Fill the cracks right up full. It works fine, if you can get at the checks. Also possible to drill holes into inaccessible checks.

  12. #12
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    Default Re: Shaft Log: questions

    Which brings up another thought - why would a shaft tube be hot? One important purpose of the cutless (when not totally exterior on a strut) is to let water in and out of the shaft tube. Obviously it will be well below boiling. Sometimes, by the way, you'll see a grease fitting tapped to the tube just abaft the stuffing box and a little line run from the cooling water exhaust (just before it enters the exhaust or muffler) to force water into the tube and flush back out through the cutless.

    I must say, I've never seen a boat with a normal length shaft (under 20 feet or so) where the shaft was supported in three places, never seen a forward cutless, and even for a pretty rigid boat it makes no sense to me. For any normal wooden boat, even the tightest mount and couple and most perfect allignment has vibration that will shred the forward cutless. I should think.

    But then, different boats, different longsplices.

    G'luck

  13. #13
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    Default Re: Shaft Log: questions

    Thanks all: But that was my thinking entirely, to prevent any wiggling with a 2 cyc Kabota diesel with soft mounts; by securing the shaft log with two cutlass bearing , prop end, the other attached to interior floor. The Landrop Gen 11 shaft seal, is only a shaft seal, my limited mechanical thinking was that one cutlass bearing will have a wiggle at the prop end. And if I can engineer a CV joint right below the Hurth tranny, It should be overkilled. Since I have a skinny deadwood keel, my mistake, perhaps a thin outer shaft log made of metal would be better than a hard plastic or FG log, just matching all components and then making a jig for the bore out of @ 2 inches. It's a 1 1/4 SS shaft.
    Again it's difficult around here, as no one builds WB's down here, up NE I could come visit a shop or shipyard.

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    Default Re: Shaft Log: questions

    Quote Originally Posted by chuckm View Post
    But that was my thinking entirely, to prevent any wiggling with a 2 cyc Kabota diesel with soft mounts; by securing the shaft log with two cutlass bearing...
    You're over your head here. Having designed a lot of marine drive trains over the years, I'm getting a bit concerned about the amount of home brewing going on here and on other forums. These are some expensive components and hard to modify later. There are a lot of pitfalls. This is an area where people need to either do what a competent designer drew on the plans or obtain professional advice.
    Roger Long

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    Default Re: Shaft Log: questions

    If you want to stop the shaft from "wiggling" you have to stop the engine from wiggling it. Which means hard-mount the engine. If you want the engine to be able to wiggle (vibration damping), then the shaft has to wiggle with it, at least at the engine end. If you draw this out with chalk on your floor, you'll see that 1/4" of wiggle doesn't change the angle of the shaft very much if the beaaring is six feet away, but it changes it a lot if the bearing is eight inches away. That simple fact of geometry is what makes the system I described above work.
    If you want to go another way, you can install an Aquadrive or Evolution shaft system with roller bearings, lip seals, thrust bearings, yadayada. At the forward end of that system you can go to a drive shaft with no thrust on it, universal joints, slide couplings, just like a rear wheel drive car's drive shaft. But that's a VERY expensive approach.

  16. #16
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    Default Re: Shaft Log: questions

    Yes, over my head and going down for the 3 rd time. Which is why I have'nt done any real bulding or drilling yet, instinctively I believe in " make mistake slowly". But do not be to alarmed: as The Kabota diesel came out of a sunk fiber glass sailboat from one of the hurricaines, paid 150$. The Lansdrop Gen 11 seal I found on ebay for a pitance, The SS shaft I traded extra lead for, and the Hurth tranny also found on Craig list for @ 250$. So far wife is still clueless to above expenses, thats the real danger. I did see two Cutlass bearing on E-bay, Doris or debie, any way 1 1/4 inch for 49$ apiece so all is still in real of mad money. Mad as in crazy being the pretence statement.

  17. #17
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    Default Re: Shaft Log: questions

    Ian,
    I was a little surprised just a week ago when talking with the head engine installation guy at Billings Diesel, in Stonington, ME. If you look at their website
    http://billingsmarine.com/
    I think you'll agree that they do all kinds of work on a remarkable variety of vessels.
    Anyway, his preferred shaft installation in a lobsterboat or dragger is a cutless bearing at each end of the shaft tube, hard-mounted stuffing box, hard-mounted engine. I inspect lots of small commercial vessels on the Maine coast, and see that arrangement some. It's certainly how it was done on every single large commercial vessel (research, cargo, towing, tanker) that I've worked on or inspected.
    Which doesn't mean that I'd recommend that approach, but if that's what a guy wants, it can be made to work. There isn't a lot of room for error.
    Day before yesterday I was talking to Glen Holland at his boat shop:
    http://www.maineboats.com/boat-launchings/muskrat
    asking him about how he does boat installations. He's a soft mount engine & stuffing box guy.
    I've personally had good luck with this approach, particularly in sailboats. All of my professional training was acquired while growing up on a farm in Minnesota, but over the last 30 years I've installed, operated, repaired, owned, and surveyed a lot of machinery installations. So I try to keep it as simple as possible.
    As far as the boat under discussion in this thread, I must admit I don't know what a John Gardner "Garvey" looks like, and the one very small picture isn't very informative.

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    Default Re: Shaft Log: questions

    Chuck, Have you found the Buck Algonquin website/catalog? They have some tubes, and I'm sure if you speak with them live they can help you navigate the challenges of your build. You really dont want to build some swiss watch system here, one stern bearing, a stuffing box to keep the water on the outside. Align your engine to the face of the shaft coupling, and you are off to the races, soft mounts work just fine, it will outlast us all... Cheers, BT

  19. #19
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    Default Re: Shaft Log: questions

    There are four specifications that the "Debbie," "Dinah," nomenclature covers:
    1) Shaft size
    2) Outside diameter (inside diameter of any bearing carrier you have)
    3) Length
    4) Material. The outer tube can be brass or FRP
    I don't think $49.00 is a bargain for a cutless bearing...

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    Default Re: Shaft Log: questions

    seo, Billings is certainly tops. I'm not a mechanic, just a sailor and aside from tug boating (and not in the engin room), driving launches and a season of charter fishing, I've little power boat time. Perhaps it's that sail boats have such different problems. It would be interesting to see if they treat the relatively light engins and light loading of an auxillary, where the engin might be called on to work at 45 degrees heel, differently.

    I'd not thought to ask chuckm what sort of boat - just projected on the basis of my mechanically limited but in the rhelm of auxillary sail to 20 tons pretty extensive experience. Goes to show the limitations of not having a systematic and broad training.

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    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    I was talking to Glen Holland at his boat shop... He's a soft mount engine & stuffing box guy. I've personally had good luck with this approach..
    So have I. These three boats, starting at 1200 horsepower, all have a single bearing in the strut with the engine waggling around on soft mounts. No flexible couplings, just a standard hard coupling at the transmission and a flexible stuffing box. The first is going on two decades of service and being repowered, last I heard, at Billings. These boats are remarkably smooth. I have a video of one somewhere with a cup of coffee sitting on a quarter bit while running at 20 knots and there aren't even any ripples on the surface of the coffee.







    Same set up as most sailboats including my own and hard to beat. Boats like lobsterboats with their engines well forward can't do it because there is a limit to how much shaft you can have between bearings. Once you've put that second bearing in, you have to either hard mount the engine or go to complex flexible couplings and Aquadrive like setups if you want to prevent transmission of any but just the highest frequencies. I've often gone up on shaft diameter just to be able to retain this simple shaftline arrangement. A larger shaft is way cheaper than all the other stuff involved in a two bearing set up. However, with a forward engine location, the shaft gets too large.
    Roger Long

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    Default Re: Shaft Log: questions

    Seo, How does it work with a cutlass bearing forward of the SB? It would be dry!

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    Default Re: Shaft Log: questions

    Wiz, If a boat has a long section of unsupported shaft, think fishboat, down in the shaft alley, etc it can have intermediate bearings, sometimes called pillow bearings, the ones I've seen and worked on are iron or steel housings that is shimmed and bolted to floors, with greased roller bearing insert. The whole thing obviosly needs to be aligned well. I have seen one or two water cooled bearings at the forward end of shaft tubes, and they have been trouble in those few instances, not enough water flow in this area in my estimation... Certainly not needed in a boat with a 4' shaft length... Cheers, BT

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    Default Re: Shaft Log: questions

    Boattruck has it right. They're often called carrier, or intermediate, bearings. Babbit pillow blocks were pretty standard, replaced with self-aligning ball bearings. The virtue of the babbit pillow blocks is that they were in two pieces, so could be replaced (or new babbit metal poured in situ), without sliding a new bearing the length of the shaft. Now then have two-piece roller bearings that can have a two piece housing, so easy to replace. Absolutely not needed for a 4' shaft.
    Here's a picture of a typical shaft installation in a lobsterboat. Soft mounts, FRP shaft tube. The stuffing box will be a self-aligning box on a rubber hose, not yet installed. B-model Cummins, ZF gear. The open mount hole on the back of the gear is for the power steering pump, I think.
    SEO
    http://s1191.photobucket.com/albums/...t=IMG_0100.jpg

  25. #25
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    Default Re: Shaft Log: questions

    Nice looking boats, Roger. Are those alu hulls?
    Mainly I'm fooling around with pasting pictures right now, but here's a kind of interesting picture.

    http://s1191.photobucket.com/albums/...t=IMG_0062.jpg

    I'm not having much luck with this attaching pictures business. In the post above it linked all right, but didn't display the picture, even though I selected WYSIWYG. This is even worse, but if you past the url above into a new window it ought to display.

    This is a picture of the stern bearing and prop of a sistership of the Holland 32 pictured in post #24 above. You'll notice that there isn't a stern bearing housing bolted to the back of the keel (sternpost, whatever you'd like to call it...) Instead, Holland simply takes the FRP stern tube, and glasses the stern bearing to the back of it, then installs the tube and bearing into the hole bored through into the hull, and builds up a strong FRP laminate around the bearing. There are a couple of set screws threaded into the FRP, and nosing into the bearing liner. The drill for replacing the bearing is to pull the shaft, put some dry ice into the bearing, and warm the outside. That gets it out. To install the new bearing, put it in the freezer overnight, warm the housing with hot water, and slide it in.
    This is a pretty aggressive approach to reducing the turbulence around the prop. The rather elaborate 5-blade prop in the picture is turned by a 425 hp Cat 3126, and will go over 30 kt.

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    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    I'm not having much luck with this attaching pictures business.
    It's dead simple. Just type "[img]" in front of the link and "[/img]" directly after it. You have it right in your post but typed "url" where you should have typed "img". Either that or you clicked the link button instead of the image button. Easier just to type directly.



    Yes, those are aluminum boats, part of my 80-90% market share in additions to the coastal research vessel fleet over the last two decades. They also have 5 blade props and single struts. I'm with Glen on clean flow to the props. These two boats that you've probably seen have their skegs offset outboard of the props with single struts so you won't have all that structure slowing down the water to the wheel. The smaller one went a knot faster than predicted. It also makes them more likely to shed pot warps.





    Note in the second picture that can be clicked to at your photobucket site that the coupling is a plain steel coupling. No flex coupling or even a Drivesaver. That's the way you do it folks.
    Last edited by Roger Long; 12-03-2010 at 08:54 AM.
    Roger Long

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    Default Re: Shaft Log: questions

    Thanks for the link tips, Roger. Still practicing. Here's another photo of the Holland boat:

    [img="http://s1191.photobucket.com/albums/z477/se02/?action=view&current=IMG_0107.jpg/img]

    Some other good things about this installation are:
    1) Use of a split shaft flange. Also sometimes called a "Kahlenburg" coupling, because that was the company that made them. In this design, the shaft is clamped into the coupling by the pair of heavy bolts that run perpendicular to the shaft. By loosening the clamp bolts the flange can be taken off without needing a three-jaw gear puller, which can be very hard to use in the space often found around the back of a marine reverse gear.
    2) The use of welded aluminum angle brackets that are bolted to the inside of the engine beds, instead of just fitting the mounts to the top of the beds. This has several good results:
    a) The brackets can be easily adjusted up and down by drilling new holes, which can be very useful when repowering a boat.
    b) The beds can be deeper, which adds longitudinal rigidity to the hull right where it's needed, under the heaviest item in thos (engine).
    c) The beds are set wider, which makes access better. When the beds are set in right under the engine mount brackets they impinge on the starter, and often on various pumps and coolers that are often mounted down low on the engine.

    OK, now we'll see if the link works...
    SEO

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    Default Re: Shaft Log: questions

    Try that again...
    [IMG][/IMG]

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    Lightbulb Re: Shaft Log: questions

    EUREKA!!
    High fives! Pats on the back!! Senility postponed!!

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    Default Re: Shaft Log: questions

    "Kahlenburg" couplings are an extra cost option, but unless you have really good access to the back of the engine they're worth the price.

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    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    Some other good things about this installation are:
    One that I would question though is how high the engine appears to be jacked up on the mount screws. Some adjustment is required but going all the way to the top puts a lot of leverage strain on the mounts in a high power installation. I would put some shims under those mounts.

    When I lived in Friday Harbor WA, one of the fast gillnetters did a show off departure opening up suddenly to WOT in front of the fuel dock. There were loud rumblings and clashing noises and it sagged back in the water and limped back to the dock. It's engine had been cranked up right to the top of the coupling bolts and it had simply bent them over!
    Roger Long

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    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    Try that again...
    Almost. You've got the img tags in twice which is why it says "[img]" on each side of your picture. Just put them in once and you're there.
    Roger Long

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    Default Re: Shaft Log: questions

    With the bracket arrangement as pictured above it's easy enough to put in a spacer block between the bed brackets and the soft mounts if one wanted to bring down the height on the bolts. From the fact that there's no exhaust hooked up, no steering pump, and no couple bolts, as well as no cockpit platform, I don't think the boat is quite finished.
    In the picture attached below (I'm gonna get my 40 hours in on this photobucket stuff...):



    The boat in the foreground is the one with the stern gear that's pictured above. The boat in the background is the infamous "Red Baron," which belongs to Glen Holland's father, Corliss Holland.

    Before retiring from racing, the Red Baron held the title of "World's Fastest Lobsterboat" for several years, with a record speed of 57 knots. It's powered with a bored and stroked 460 Ford with a supercharger, probably producing around 600hp.
    In the time I've known the Hollands, the Baron has had a straight-drive engine, a vee-drive, and a remote-mounted vee-drive that allowed putting the engine right in the stern.
    The point is that if Glen figures those mounts will hold up, my guess is that they will.
    Aside from that, the boat with the Cat engine only has a 1.8:1 reduction gear, so I doubt it will have the hole shot that a gillnetter with a big prop might have.

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    Default Re: Shaft Log: questions

    Great thread guys. Thanks for sharing your expertise! I hope you don't mind me to try and wring another tidbit out of all this. In this picture, are the prop nuts on the shaft in the proper order? or should the half-height nut bear against the prop hub?


    Thanks
    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Shaft Log: questions

    Here's what I get from this source:
    http://www.boltscience.com/pages/glossary.htm
    2. The term is sometimes used for thin (or jam) nuts used to lock a thicker nut. When used in this way the thin nut should be adjacent to the joint surface and tightened against the thick nut. If placed on top of the thick nut the thin nut would sustain loads it was not designed to sustain.
    I can't say that description is completely clear to me.
    In my somewhat anti-technical experience, any two nuts, thin or thick, will do okay, If you put nut #1 on first, and tighten it to the correct torque value, then put on nut #2, and tighten it snug against nut #1. Then Get a good wrench on nut #1, and hold it in place, and the get a wrench on #2 and yarn it against #1.
    Aside from this profound theory, it's noted that in this picture it also look like there's a cotter pin through the shaft behind Nut #2. All things being equal, I'd rather it was a castle nut.
    But all things are not equal.
    And as the man said:
    "The perfect is the enemy of the good."
    Or something like that.
    SEO

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