Shaft alignment - how to?

[cmedsailor]

Last time my shaft was aligned was 2 years ago when a mechanic installed new engine mounts. I would like to check the alignment again but this time myself. Anybody has clear and easy instructions on what to do? Or probably a link to a nice site with pictures included?
Thanks

 

[Tradewinds]

Here you go - halfway down. Very comprehensive.

Suffolk Yacht Engineering.

He's a forum member too - 'Engineer' I think.

 

[VicMallows]

Suggest an indication of your engine/gearbox and boat type would be useful.

 

[kunyang]

Take your time and do small things. Firstly, in neutral, can you turn the shaft and does it turn with the same force for 360 degrees. If it does, it probably will be ok.

Loosen off the bolts on the shaft joint a couple of turns each. And again turn the shaft 360. Put a feeler gauge between each of the four gaps so that you can feel a pressure as you put the gauge in to the same depth (this should be the same gauge and you may need to loosen further or tighten slightly until you are happy with the tension on the feeler gauge). The pressure should be the same at all points. Now turn the shaft 90degrees and try the feller gauge again. Repeat on all points of the compass.

If there is a tight side, then you have to work out which engine mount(s) to adjust, and if you get it wrong, the pinch gets worse. Always count the number of turns on the bolts, engine mounts and shaft as you can always go back to the starting point.

Be careful that you don’t raise/lower the engine and put too much pressure on the shaft.

If the shaft is slightly 'off set' this should be obviouse and the shaft will be hard to turn in all positions.

 

[Clyde_Wanderer]

Here you go - halfway down. Very comprehensive.

Suffolk Yacht Engineering.

He's a forum member too - 'Engineer' I think.

Why am I only getting a narrow vertical section of the pages when I go to this site?
C_W

 

[dash300]

Why am I only getting a narrow vertical section of the pages when I go to this site?
C_W

Me too !

 

[Tradewinds]

Why am I only getting a narrow vertical section of the pages when I go to this site?
C_W

Strange. Works fine for me on Chrome & Firefox (Mac).

 

[Norman_E]

My boat has the common four bolt flanges on shaft and gearbox. With all bolts slackened and a set of feeler gauges I found that as I rotated the shaft it was hard to tell whether it was right or not. I tried a different approach. I slackened off the bolts and inserted a thin washer which I had cut to a C shape so that I could slide it in around one bolt, then gently tightened that one. On turning the shaft so that the tight bolt was to one side, measuring the gap at the other side with feeler gauges, then turning 180 degrees and repeating I found that the difference was too small to worry about. That was a relief because moving the engine sideways would be difficult. With the tight bolt at the top, and then at the bottom a difference was revealed that indicated that the engine was either too low at the front or too high at the back. With the tight bolt down the gap opposite was wider than it was when the tight bolt was at the top. Raising the engine on its front mounts by about half a turn corrected matters.

No doubt someone will tell me that my method is flawed, but because the tight bolt stops the two flanges moving apart at one point it does make measurement more certain.

 

[MrCramp]

Why am I only getting a narrow vertical section of the pages when I go to this site?
C_W

If you click the Adobe (PDF) sign at the top of the article it will open up properly for you.

 

[cmedsailor]

Suggest an indication of your engine/gearbox and boat type would be useful.

Engine: Volvo Penta MD2030D
Gear Box: MS10L
Boat: Beneteau Oceanis 361

I don't know if it needs alignement (engine doesn't seem to vibrate) but since mounts were new I would expect that they become soft with time (but I could be wrong).
Anyway, I believe it's a useful job to know and haven't so far tried it myself.

 

[fisherman]

Theoretically it might pay to check that the shaft is central in the stern tube first. Feeler gauge as above, it should be aligned within 2 thou per inch of coupling diameter. At that point I would put a R&D coupling in, but depends on prop clearance, and the prop should not be (from memory) more than 1.5 times shaft diameter from the stern tube bearing.

 

[ghostlymoron]

There's an explanation of how to do it in Pat Manly's book http://www.amazon.co.uk/Simple-Boat-Maintenance-Yachts-Motorboats/dp/1904475027 I've never done it though. I do find Pat's book very useful although it would be better if the photos had been taken by a professional.
The Suffolk Yatch Engineering link was good but could do with some diagrams as it's a bit hard to follow. Good advice though.

 

[Ammonite]

The Beta agent I use suggests using a nylon bush to centre the shaft in the stern tube first. Works a treat (once you've made the bush of course), then use the feeler gauge method suggested earlier. The only other tip I'd add is to make sure your cutless bearing is not worn before you start. If it is replace it (obvious really)

 

[Bosun Higgs]

Engine: Volvo Penta MD2030D
Gear Box: MS10L
Boat: Beneteau Oceanis 361

I don't know if it needs alignement (engine doesn't seem to vibrate) but since mounts were new I would expect that they become soft with time (but I could be wrong).
Anyway, I believe it's a useful job to know and haven't so far tried it myself.

If it isnt broken, dont repair it! Leave it alone.

 

[fisherman]

If it isnt broken, dont repair it! Leave it alone.

Missed that. Absolutely!

 

[webcraft]

If it isnt broken, dont repair it! Leave it alone.

Agree. Your 'to do' list must be very short.

- W