Prop shaft wear, how much is ok? 0.25mm wear.

[Georgio]

Hi,
just removed my prop-shaft as a new cutlass bearing is needed.

There is a small amount of wear on the shaft itself and I have measured it as 0.25mm using a pretty accurate calliper.

Is this acceptable? not acceptable or ok for a few more seasons?

Your advice please gents (or ladies)

Cheers

 

[Georgio]

Bump to top of page, hoping that a knowledgeable forum member can advise...

 

[HunterWanderer]

I never have changed my cutlass bearing and have a clearance of about 1 mm !

There is no vibration and the boat runs beautifully under power. No wear of propshaft noticeable.

I have a Yanmar clamp type shaft coupling, a volvo shaft seal , cutlass bearing in a P bracket and a fixed 3 blade prop. Have spent a bit of time to ensure alignment when in the water though.

Cant think 0.25 mm of shaft wear would be significant.

 

[rotrax]

To put your clearance in Imperial terms for a not too high tech bit of engineering, 0.25mm is pretty much 10 thousandths of an inch.

Or, as my old friend Simon would say, about two gnats cocks..........................................

 

[Georgio]

Thanks chaps, I suspected it was close to sod-all but wanted to check

 

[Pete7]

I have a Yanmar clamp type shaft coupling, a volvo shaft seal , cutlass bearing in a P bracket and a fixed 3 blade prop. Have spent a bit of time to ensure alignment when in the water though. Cant think 0.25 mm of shaft wear would be significant.

Bit of a thread drift, but how do you check the shaft is aligned in the stern tube with a volvo seal? It was fine whilst ashore but has it changed now she is launched? or is it a case of don't worry?

Pete

 

[HunterWanderer]

Bit of a thread drift, but how do you check the shaft is aligned in the stern tube with a volvo seal? It was fine whilst ashore but has it changed now she is launched? or is it a case of don't worry?

Pete

The alignment probably has changed as the hull is evenly supported in the water rather than just at the support legs and all materials deflect under load.

Its best to check it after a couple of weeks in the water. Just disconnect the gearbox from the shaft coupling and loosen the coupling from the shaft and slide the coupling down the shaft to ensure the coupling is not engaged on a spigot.
The volvo seal holds the shaft in the correct place , so move the engine till the shaft is aligned laterally and angularly. Use a feeler gauge or calipers to measure the errors.