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Discussion Starter · #1 ·
I've got a Vetus m3.10 diesel. I was motoring a couple days ago and all of a sudden I lost what felt like 90% of thrust to the prop. Engine was running fine, at minimum throttle in gear the boat would slowly move at what felt almost normal, but any increase in throttle would result in no increase in speed, and a metal-on-metal squeal.

Thinking I got something caught in the prop I dove under and there was nothing.( I did notice however that the new zinc on the shaft behind the prop had fallen off? -might be related).

We sailed back into the harbor and was able to slowly motor to the mooring at minimum throttle.

I checked the transmission fluid, level good and clean. I just changed the transmission fluid this spring, less than 10 hours of motoring.

We were able to reproduce the metal-to-metal squeal with me under the boat, with the gear engaged and giving the prop a turn, the shaft will spin, but the coupling does not.

Back in the boat, engine running, engaging the transmission in reverse the shaft was able to be pulled back about 3/4 of an inch from the coupling, putting it in forward the shaft is driven back into the coupling.

Looking at the Vetus diagram for this coupling, it appears that there is no key? But a pin driven through the coupling and shaft. see below:


My plan is to take apart the two halves of the coupling to see what's going on inside. Did I break the shaft, or the pin that goes through the shaft? Is there a through-pin? I'm hoping that the front part of the coupling does not need to be removed as I don't have a spanner type tool that will fit that, and it looks like with a 130 lbs it could be a bear to remove.

Anyone have any other ideas or suggestions? Things to look out for? Don't assume I know anything about couplings, yesterday was the first day I've even given this thing a good look.

PS. For those who know the main coast, we were motoring around the west side of Seguin with a west wind making it an imposing looking lee shore. I was saying "this would be bad spot for engine trouble"..shortly after which we rounded the southern tip of the island and the above engine issue happened. We were able to easily pull up sail and tack away from the island, but if had happened 15 minutes earlier we'd have been in for a fight!
 

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...........Did I break the shaft, or the pin that goes through the shaft?..........
You just couldn't have broken the shaft!....Could you? The torque required to break a shaft would have been felt.

I'm betting that you find a sheared pin when you take your coupling apart. The squealing occurred when there was enough torque applied to the shaft to make the propeller turn slower that the coupling. In other words, it couldn't keep up because of the resistance of the propeller.
 

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Discussion Starter · #3 ·
You just couldn't have broken the shaft!....Could you? The torque required to break a shaft would have been felt.

I'm betting that you find a sheared pin when you take your coupling apart. The squealing occurred when there was enough torque applied to the shaft to make the propeller turn slower that the coupling. In other words, it couldn't keep up because of the resistance of the propeller.
I sure hope not. We were motoring easy, about 4 knots, pulling a dingy, not much for waves. Don't think we hit anything or got cought up with anything, we just lost power.

How often do these pins shear? is there standard sizes standard to buy new ones? My shaft is bronze (possibly old) and when the new engine was put in they used a stainless pin..corrosion? I just hope I can get that coupling apart to see. I also expect that driving a broken pin out could be a difficult. Although, a broken pin is better than a broken shaft.
 

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I agree with Selkirk, most likely you broke the Shear Pin.

You can test this with the Engine OFF. Put the Engine in gear and with a Pipe Wrench (or Vice Grips) try to turn the shaft on the other side of the Coupling.

You will need to remove the spanner nut if it turns out the pin is broken. (This can be done with a hammer and a flat head screwdriver if there is room.
 

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Discussion Starter · #5 ·
You can test this with the Engine OFF. Put the Engine in gear and with a Pipe Wrench (or Vice Grips) try to turn the shaft on the other side of the Coupling.

You will need to remove the spanner nut if it turns out the pin is broken. (This can be done with a hammer and a flat head screwdriver if there is room.
This is about what we did. Engine in gear, I was able to tun the shaft by turning the prop while under water. The shaft turned but the coupling did not. Where does one by these shear pins? Standard items? I'd like to go back to the boat with all the parts so I can repair this in one trip.
 

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.............How often do these pins shear? is there standard sizes standard to buy new ones? My shaft is bronze (possibly old) and when the new engine was put in they used a stainless pin..corrosion? I just hope I can get that coupling apart to see. I also expect that driving a broken pin out could be a difficult. Although, a broken pin is better than a broken shaft.
I don't think the shear pins break all that often......don't really know, but I'm betting that yours just corroded into two pieces.
If you can get to it - and you can, it's just a matter of how - it will come right out if you use the right size drift pin. If you don't know, a drift pin is sort of like a center punch except that it is not tapered and comes in several sizes. Do yourself a favor and drop in a Sears and buy a set of five or six different sizes.

And watch what you use for a shear pin. If you find your shear pin is all corroded, then someone found a material that should never have been used. I'd have to study up myself before I selected the right material, so I really can't offer advice there, but you'll know what size shear pin to get by what size drift pin fits into the hole.

BOL!:)
 

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D=Diameter of prop shaft in MM
A=Diameter of pin and drill bit to drill outin MM
B=diameter of drift pin to use in MM
Just measure the diameter of the prop shaft and you are home free.
 

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Some things to remember when trying to remove the old pin.

Since the shaft has spun in the flange the holes will most not be aligned so that just drilling straight through will not be an option.

You might get lucky and find some kind of alignment marks that will clock the flange to the shaft and maybe try just knocking the pin through in three pieces.

You may have to slide the spider off and remove the broken pin that way.

Looking at the digram closer it looks like there is a key at the 6 O'clock position on the spider and 12 O'clock on the drive flange.
 

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AND---

It looks like they want you to torque the collar nut to 210 foot pounds so you had better get a wrench and a pipe.
 

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Discussion Starter · #10 ·
Well, came apart easy. No shear pin. There's a set screw where the diagram says the pin should be. And the collar that requires the 130 lbs was very loose. Light tap with a hammer & screwdriver and it ws free. I've got a proper hook spanner wrench on order.

Thanks guys.
 

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Well it looks like THEY didn't use a stainless pin now does it.

I think (after re-reading and looking real hard at the diagram) that you have a TAPER LOCK type bushing.

That nut on the back is what keeps it on and tight to the shaft, that is the reason for the high amount of torque required.

Be sure you use the proper grease on the nut and taper but no lube on the shaft.

I think that if you had just tighten the nut all would be well.
 

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Me thinks you math is upside down--
130# at 20 inches= 2600 inch pounds
divided 12==217 foot pounds

It's late and I'm tired so I could be wrong.

I believe that 130 lbs at 20" is only 78 ft-lb torque.


Pat
 

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#1 What is the diameter in millimeters of your prop shaft?
#2 do not use a woodruff key.
#3 you have to drill a hole either either 8 mm or 10 mm through the shaft.
#4 you insert a pin either 8 or 10 mm into the hole, With a smaller drift punch either a 5mm, or a 6mm and tap it in with a hammer.
#5 Re-assemble, and using your new spanner wrench, that is 20 inches LONG, use your foot, and stand on the wrench using about 130 pounds of your weight. if your wrench isn't long enough put a pipe on it and measure 20" like the picture, and stand on it.
There you go, have fun.
 

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Discussion Starter · #14 ·
Hey Everyone,

I'm still dealing with this. My coupling has a hole with a cup point set screw (allen head). Thinking there must be a hole in the shaft the set screw sits in, I was able to move the coupling up to expose the shaft and there's no depression or hole. There is a long slot running a few inches up the shaft that's a bit mangled as if the set screw could have been jammed in that. I can't see how it would hold for fore and aft movement though.

I did get a proper spanner wrench, and tightened down that lock collar as best I could, however had difficulty keeping the transmission from turning. Putting it in gear wasn't enough. That said, I was able to put enough pressure to give the engine a good twist on it's rubber mounts. The shaft spun & moved forward in the coupling within minutes in use when put into forward gear.

I really need to drill a hole for the set screw as some have advised, or a hole straight through and pin it.

About the hole. I'm thinking it will be difficult to drill a perpendicular hole through a bronze shaft while the boat is in the water. I could rig up something to brace the shaft under the drill, but keeping the drill centered?

I've seen some drilling jigs somewhere that clamp on to a cylinder, and align the drill bit..but where? Anyone know of anything like this??

And if I choose to drill straight through? Where do I get a pin? "Shear pins" I've seen are small and short. I need something around 3.5 inches long. The best I could come up with would be to order some 1/4 inch bronze rod and cut to length. My shaft is 7/8 inch (measured w/o calipers) so I could use a 1/4 drill bit.

I'm leaning on drilling a hole for the set screw to fit into, however, if I were to drill straight through, I could use the hole in the coupling as a guide..but then I'd need to drill straight through the shaft and the other side of the coupling, or else how would I ever get the pin out to dismantle.

Thanks for reading so far. With the boat on the water, I'm going slow with this. Don't want to mess this one up.

Any suggestions appreciated.
 

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Discussion Starter · #16 ·
Possibly. I've not dealt with a key's shaft, I'm assuming that's what I'm looking at.

Although the slot is fairly long in the shaft.

One thing I'm dealing with, is a tight tolerance at the prop. If the shaft is pushed forward under forward thrust more than 1/8th the zinc donut rubs, if the shaft us pulled back 1/4 inch it will hit the inside of the rudder at maximum turn.
 

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Why re-invent this? Why don't you just follow the directions? Don't you think they made the directions and sizes for a reason? Maybe this is beyond your capability. Spend a few dollars, and let a reputable person repair this for you. Then GO SAILING, and sleep well knowing you didn't half ass this together, putting your crew and others in peril because of YOUR decision. By the way, if you look at your drawing, the keyway with the BIG X means NO, as in "DON'T USE A KEYWAY!"
 

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Discussion Starter · #18 ·
Thanks Capnblu,

I appreciate your sentiments. I'd be happy to write the check that gets this done. I did ask around to some mechanics, and so far no one I've talked to has seen this setup before, or expressed that they knew just what to do. I could pay someone to drill the hole, then what do we use for a pin? I've got a call in to Vetus on that issue. We'll see what they say. I'm thinking 1/4 inch bronze rod.

If the boat were out of the water, I could remove the shaft and just use a drill press. In the water, laying over the engine, holding an electric drill, I'm concerned I won't have very good control.
 

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I would not go back to the set-screw arrangement. It has already failed you once. The correct installation method is shown fairly clearly in the diagram.

The shaft probably came with a "key" slot already in it. That's why you see the slightly mangled slot that the set screw was set into.

Keep pestering Vetus. They should be able to provide the shear pin for their own transmission. As others have said, follow the diagram, i.e. 8mm bit, 8mm shear pin, 5mm drift, etc. (or whatever it indicated). I would think with a sharp bit and some solid bracing, you could manage with a hand drill -- but I haven't seen the space you're working in either.

Good luck. Sorry about the troubles, but glad it didn't act up until after you had safely passed that lee shore.
 

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How I would go about this repair with the boat in the water.

1 Re assemble the coupling without the nut and collar on the prop side, tighten the 4 through bolts. This will align the cross in the coupling.

2 Install the zink on the prop shaft and align the prop in the proper location. This will align the prop shaft in the cross.

3 Mark the shaft at the exposed end of the cross on the prop end for reference. Sharpe??

4 Disasemble the coupler, shove the lock nut, collar and coupler twards the prop and push the shaft back and remove the coupler half connected to the transmission.

5 Find a drill bit that will fit snug into the set screw hole, that will be you guide. Realign the cross to the mark. Drill the hole 90 degrees to the keyway.

6 Drill your new hole out to the correct pin size.

7 Before you start reasembly make a tool using a length of angle iron (1 1/2?)to hold the coupler while tightening. Use the engine side of the coupling as a guide and mark two holes that hold the coupling together at the shortest distance (not accross the center). Make sure it fits, you may have to clearance for the shaft. Drill the angle so you can use it to hold for loosing too. Be sure it is long enuff to reach to the hull or accross the sole or some thing so that when you go to tighten the spanner nut it will hold the torque and not the engine. You can always cut it shorter later.

8 Assemble the coupler with the holding tool will be pushing aginst something solid and tighten the four bolts first.

9 Now get out your spanner and a piece of pipe and apply 216 pounds of force at one foot (12 inches) from the center of the shaft.

10 Go back and remove the holder and install the two bolts and you are done.
 
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