Putting that engine back on the saildrive

[ProjectManaia]

Hello everyone and thanks in advance already!
I had to take my kubota 24kw engine off the saildrive (old yanmar, is all the detail i know) to change a busted flex coupling in between, no problem so far. But now i cant get the engine with the coupling back o to the shaft of the saildrive since it all has to be on a slight angle with engine mounts etc.
Is there some geniius trick i am not aware of?
Thanks already.... been stuck hiding from a storm for days not being able to fight it with one engine today it finally calmed down enough to work on it....

[Dulcesuenos]

You need to adjust the mounts on the engine to get the SD shaft as close as possible to the hole in the dampening plate. Grease the shaft well and slide it together. Not sure what engine ours only had two eng mounts and one SD mount so it was necessary to lift a teeny bit on front of the SD to put it at its normal angle. Not easy with room for just one person but not horrible either.
If the angle is way off it is possible to create a leak on the SD seal.

[ProjectManaia]

Originally Posted by Dulcesuenos

You need to adjust the mounts on the engine to get the SD shaft as close as possible to the hole in the dampening plate. Grease the shaft well and slide it together. Not sure what engine ours only had two eng mounts and one SD mount so it was necessary to lift a teeny bit on front of the SD to put it at its normal angle. Not easy with room for just one person but not horrible either.
If the angle is way off it is possible to create a leak on the SD seal. Also a good time e to replace that seal while waiting

Thank you!
I kept trying and trying and after rigging a little plley system to lift front and back end of the engine things were easier...
Another attempt tomorrow since something gave in again....

[tkeithlu]

It seems like every description of how to align an engine with a shaft leaves out one dimension - what to do when you find that the engine connection is to port or starboard of the shaft connection, when you've dealt with height (including the shaft sag described by Dulcesuenos above) and the gap being even all the way around. The engine and the shaft are parallel but not on the same line. The trick then is that the engine mounts are below and to the sides of the engine line, so you roll the engine by lowering the mounts on one side and raising them on the other.

[Ostinato]

How is the sail drive stablized? Sounds it may have moved. I would focus on shifting it as well being very careful to not let get away from you. Without pics it is hard to know to suggest but if you don't have wedges between the SD mount and the drive that one place to work. If can you vertically suspend it that's another.

[ProjectManaia]

Alright, so putting the engine back worked out but the real issue seems to be somewhere else. The joining piece (flex coupling?) Not sure what it is called, had snaped and i put a replacement in, which snapped again after few hours runtime.
Both times it happened during motoring at constant 2300rpm in gear, not during shifting.
I am not sure why, since this is a new issue to me.
Any thoughts out there on why this could keep happening?

There was nothing on the prop or anywhere else tangeled so i am a little puzzeled to be honest.

Very grateful for any advice!

[tkeithlu]

Something is not aligned, so the piece is flexing with each rotation until the fastener snaps. The couplings should have only torsional and thrust loads on them, but yours appears to be stretching and compressing at all three points that failed. The only other answer I can think of is that the coupling wasn't tight to begin with, but I doubt that you started it up with loose bolts.

[tkeithlu]

I'm also a little puzzled following a closer look at your photos that you appear to have six bolt holes and to have used three.

[tkeithlu]

Back with another cup of coffee. Mistake: that's sheer load absorbing torsional load, not torsional load itself, but correcting my wording doesn't help much. This is not what i would call a flexible coupling - they are big plastic doughnuts that don't work harden and then snap, otherwise called metal fatigue. This connection looks like it needs very good alignment, and very little play in the bearings for the respective shafts. You could have what appears to be very good alignment but have a wobbling (eccentric) shaft once you start turning the prop. Has anyone else got another idea?

[ProjectManaia]

Thanks for the input so far!
Only three holes and bolts were used, that is correct, but also on the flywheel there is only 3 holes to secure to....
The most important question for me right now is how to fix it?
Align better? If so how? Or get the rubber donut flexible coupling? Will be difficult to source here and probably needs to come from bangkok....

[tkeithlu]

OK. I'll take a try at it. Another two cup morning. Others with things I miss, please step in.

1. Determine that the propeller is stable. If you can shake it in its bearings, they need to be replaced.

2. Determine that the engine is firmly mounted. If you can shift it back and forth by hand, the engine mounts need replacing. Also try lifting it with a pry bar. Don't force it, just see if it lifts when you are applying a force to balance its weight.

3. Hold, as straight as possible, the propeller shaft. This probably means slightly lifting it, unless it has a bearing very close to the junction. Check this by placing as long a straight edge as possible along it, and as you rotate the shaft in stages, look for any gap or bridging between the straight edge and the shaft. If it takes more than a force equal to the weight of the suspended end of the shaft to straighten it, you have a bent shaft.

4. Be sure that there is no play in the shaft coming out of the tranny.

5. With the two flanges touching, use a feeler gauge to determine whether a gap exists between the two on one side but not the other. If you don't have a gauge, use a sheet of paper. Turn both engine and propeller shafts and see if the gap stays in the same place. If not, something is bent.

6. Adjust the engine location by loosening the nuts above the engine flanges, and turning the nuts supporting the engine. Think that you are trying to make two centerlines (shaft and engine) into one line, and how the engine has to move to achieve that.

7. Use your straight edge again to determine that the edges of the two flanges match. The engine line could be parallel to the prop shaft, but displaced from it up, down, left, or right. Again, adjust the engine as needed.

8. Tighten the top nuts on the engine mounts while holding the bottom nuts still with another wrench. Then go back and determine that alignment has not changed.

9. Use high quality bolts, lock washers, and nuts. Tighten the bolts joining the flanges in rotation. If one bolt turns farther than the others to tighten, you are bending something. Equalize the torque on the nuts.

10. If you have a way to do it, measure run out, that is difference in distance between the side of the shaft and some rigid point, as you turn the engine.

11. Cut a notch in the end of a piece of wood about the dimensions of a ruler. Start the engine, put it in gear (check your mooring lines!) at idle, and hold the notch against the propeller shaft. If the end you are holding vibrates rather than running on a smooth surface, something is not aligned or is bent or a bearing is bad. You can do this step with your finger, but it's dangerous.

12. Get under way and repeat #10. smooth, no vibration, the job is done. Vibration, and something (prop, perhaps) is bending the shaft and as a result your coupling.

All said, I am a fan of plastic couplings and plastic thrust plates (where those three springs are in your pictures). They do relieve you from having to be perfect. Perfect here means that doing an alignment out of the water is not wise - boats flex when you support them with water rather than keel blocks. Good luck with it.

[tkeithlu]

Oh. Be sure that the bolts that you use to join the flanges fit the holes with non-threaded shaft extending into the second flange. If the two flanges can figure out a way to move relative to each other, they will. Finally, my mantra:

Never Let Anything Mechanical Know That You Are In A Hurry.

[tkeithlu]

Notes: in #1, that's the propeller SHAFT that needs to be stable.

It is possible, but unlikely, to misalign the flange on the end of the propeller shaft. If when you rotate the propeller shaft the gap goes around the flange rather than staying in the same place, it's not on straight.

[jimbunyard]

Where did you get that 'flex plate'? I'm not familiar with the Yanmar saildrives, but it they're anything like any of the others, the shifting/clutching is done inside the gearbox of the drive. The plate you have looks like a clutch disc, hence the friction lining on the outer perimeter.

A proper flex plate will look something like this



and is indexed so the center spline is aligned with both the crankshaft and the input shaft of the gear. There are also depth issues; if the depth isn't correct, pressure can be put on either the center hub of the plate and/or the input shaft bearings, which can cause the failure of either.

The holes for the rivets retaining the friction lining are not indexed to the centerline of the crankshaft and can be (and probably are) easily far enough off center to both make the stabbing of the saildrive difficult and to cause the hub to fracture exactly as seen in the pictures.

If I'm wrong and there is some kind of clutch mechanism used with your saildrive, my apologies and please disregard.

[tkeithlu]

Jim, you're on to something here that bothered me but I then put aside in thinking about the alignment task. That plate looks like a clutch, not a connecting flange between tranny and shaft, and should turn relative to a similar plate and have a spring that holds them together and a lever to separate them. Or, it's used as an automatic clutch and just slips a bit with gear changes. In any case, they would not be bolted together. The part in the center looks like the thrust (or flex) plate. Something is not assembled correctly here.