Permissible wear on prop shaft at bearing replacement

[bluerm166]

The attached shows a survey along our prop shaft - apparently a 25mm metric dia. The end of the exg. worn brass / nitrile bearing ,not yet drawn out,shows 38.2 o/d,so presumably imperial. Replacement is considered because of the noticeable play that allows the shaft to be lifted manually .I can see that I can find a 25 metric x imperial o/d bearing .
There appears to be wear on the shaft at the cutlass position that would give quite a starting tolerance for a new 25mm bearing.The shaft is apparently running true.
There is some marked wear at the position of the stuffing box gland ,but it is not scored and can be adjusted to a drip.
What is the opinion please of the starting tolerance, varying between 0.34 mm and 0.1 mm plus the tolerance on the nitrile ,bearing in mind the nuisance involved in changing the bearing ? The existing bearing has lasted 5 years.

 

[Plum]

The attached shows a survey along our prop shaft - apparently a 25mm metric dia. The end of the exg. worn brass / nitrile bearing ,not yet drawn out,shows 38.2 o/d,so presumably imperial. Replacement is considered because of the noticeable play that allows the shaft to be lifted manually .I can see that I can find a 25 metric x imperial o/d bearing .
There appears to be wear on the shaft at the cutlass position that would give quite a starting tolerance for a new 25mm bearing.The shaft is apparently running true.
There is some marked wear at the position of the stuffing box gland ,but it is not scored and can be adjusted to a drip.
What is the opinion please of the starting tolerance, varying between 0.34 mm and 0.1 mm plus the tolerance on the nitrile ,bearing in mind the nuisance involved in changing the bearing ? The existing bearing has lasted 5 years.

I have replaced cutlass bearings when the wear as reached 1.0mm yet there had not been any vibration problems. As long as the shaft surface finish is good I would refit the shaft.

Www.solocoastalsailing.co.uk

 

[Minchsailor]

If needed a new shaft is not that expensive. T J Norris.

316 Marine Grade Stainless Steel Propeller Shafts

 

[bluerm166]

Many thanks.Will talk to T Norris and then decide.
Seems the wear forward on the bearing area is down to the (old Yanmar ) engine movement and the shaft is tending to lie on about half the bearing - the rear half so only about 37 mm - not very much ,rather than a typical 100mm.

 

[Neil_Y]

A new bearing would have a clearance of 0.12mm and we suggest change when it approaches 0.6mm
Starting with a larger clearance just means faster wear. I'd look at a new shaft.