Engine/shaft alignment

[saltyrob]

Hi Folks

Have fitted new cutlass bearing after wearing one out in 2 seasons,ouch. Should I check the shaft alignment when the boat is afloat as she flexes in her storage cradle.The boat is fitted with a Volvo shaftseal and a folding prop.

Many thanks for advice

Robert

 

[macd]

You seem to know the answer already. But other than misalignment, the bearing wear could also indicate a bent shaft.

 

[robind]

Yes! do check it when the boat is afloat

 

[Juggler7823]

I suspect you have more investigation to do. The Volvo shaft seal is not good at supporting the weight of the shaft. The shaft needs to be centred in the tube for true alignment. Also is the prop opening properly, does it vibrate? Are you on a drying mooring/silty water etc

 

[old_salt]

Check the shaft for rotating true preferably out of the boat and between centres. Re-fit and and check for free rotation with the shaft seal in place. If removal is not possible then rotate the shaft if there is any out of true you can see, or use a clock gauge on the ends of the shaft, if no clock gauge is available a suitable fine pointed flexible saw blade securely clamped and set so as to just clear by the thickens of a thin piece of paper on the end of the shaft, then rotate it the small gap should not alter, do both ends. An out of true by less than 10/15 thousandths of an inch, ie three times the thickness of a peace of paper will be of no consequence but an appreciable amount say 1/16" or more would require the shaft to be checked and possibly straightened be an engineering work shop Leave the gear box final drive and shaft flange free, when you have re-launched set up the engine to the shaft coupling with feelers or better still an engineers clock gauge clamped to one of the flanges and rotate round the outers and between the flange faces to the manufactures recommended settings if available, if none available set up so the flange faces are true a set of feeler gauges or a thin piece of flat tin cut at 3" x 1/2" will do, it needs to feel the same when pushed in between the flanges top, bottom and side to side. A short straight edge ie engineers Square stock on and across the flange faces top, bottom, side and side. Adjust the engine/gear box mounts up /down till you achieve this setting. There may not be any appreciable movement side to side of the engine, but it should be enough to line things up. The above is assuming the engine and gear box are one, if your engine and gear box are two units then it is a completely different ball game.
It may be necessary to apply some off set but I could not recommend that without seeing the set up and manufactures instructions.
If there is an engineer on your yard he may be able to advise. Setting up true and checking by running up for 1/2 min then progressing for longer to see if all is well for vibration and heat in the bearing housings is one way. Some small off set adjustment may be necessary this is to allow for rise and throw of the engine when it is running and on load but this amount will be more by experience than anything else unless it is stated in any engine /boat manufactures instructions you may have, then re check for any vibration. It should all run smooth and sweet. PS make sure she is well secured on her mooring
To be honest it is very difficult to explain all this and keep it making sense. If you have any concerns after my original set up suggestion ie set up true when in the water then I strongly advise an engineer have a look.
I do hope this has made some sense and helps.
PM me if you wish, a chat on the phone may make more sense of it.

 

[old_salt]

Also check out the post lower down index page.

Engine allignment - help needed please stevie_b