cutlas bearing wear

[saltyrob]

Hi Folks

I have a small amount of play between the prop shaft and cutlas bearing, which I replaced at the beginning of last season. Can you tell me how much play is reasonable before the bearing has to be replaced. Replacing it is a major job as the shaft is obstructed by the rudder neccesitating removing the gearbox and pushing the shaft up into the boat. /forums/images/graemlins/confused.gif

Many thanks

Rob

 

[brianhumber]

You do not say size of shaft but assuming about 1'' diameter should should not get significant wear in one year. One persons waggle is another mans tight fit. What you must appreciate is that the bigger the clearance the faster the rate of wear and the more movement you get at the shaft gland leading to excessive wear rates on this.
If your small amount is less than half a mm which can feel a large gap, I would record and monitor next year. Might pay to double check the alinement of the shaft if you had the gearbox out last year.

B

 

[steve_cronin]

Re: cutless bearing wear

(Sorry, I had to change your spelling!)

There is bound to be some free movement as it is lubricated by a film of water, Bearing manufacturers are generally unwilling to give exact details of clearances like are quoted for piston ring gaps but are often willing to discuss the matter. Since the fitting of a new bearing, especially one with a tufnol shell will result in a reduction in size and therefore clearance, it is difficult to be exact. Then there is the effect of calcification on the shaft, especially if you can't withdraw the shaft to clean the ridges of calcium deposit off of the shaft that will have accumulated whilst the boat was out of use.

Generally speaking, if the shaft visible nods when shaken, then it needs looking at but if it only moves a few thousandths of an inch then all is well.

Speak to :- Countrose Bearings for best advice.

Steve Cronin

 

[boatmike]

Re: cutless bearing wear

I agree Steve. Many owners worry needlessly about a bit of clearance. Often the bearing is "tight" when assembled and wears rapidly until there is a little play. The bearing surface is actually hydraulically generated, in other words the bearing itself should not touch the shaft when running. It's very difficult to generalise on clearance as length of shaft, p brackets, RPM, prop size etc allhave an effect but as a golden rule, if there is no vibration, knocking etc. and the play is not great it's probably OK and having "worn in" may well not wear further in a season. If you are not having problems leave it be and check again next time you haul out.

 

[saltyrob]

Many thanks for your advice. I'll leave the bearing in and check it when we haul out at the end of the season.

Thanks

Robert /forums/images/graemlins/smile.gif