Cutless bearing

[Seadee]

Noticed last year that I had a bit of play in the cutless bearing. How do you know when it's time to change it and what is the recommended play ? In my "bible" (Nigel Calder's epic) it says 2mm per cm of shaft diameter. My prop shaft is 40mm (4cm) so that suggests 8mm of play. Blimey, like slinging a sausage up market street !! /forums/images/graemlins/confused.gif

Any views ?

CD

 

[NorthUp]

more likely to be 0.2mm of play per 10mm of shaft diameter, giving a max clearance of 0.8mm for your 40mm dia shaft

 

[Sneds]

My missus allways gives my shaft a wide clearance /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

.............sorry!

 

[Seadee]

I've just spotted the typo ...

It says 1/16th inch play per inch of shaft diameter. That would make it 2mm per 25mm of shaft (not the 2mm per cm in the book). So for my MF805 (40mm) that makes about 3mm of play (1.5mm per side).

That looks more probable ?

I'll have to e mail the guru, he'll be well jarred off !!

Seez ya

CD

 

[brianhumber]

Cannot believe anybody would think or write that 2mm clearance on a 10mm shaft is acceptable, total rubbish - must be a typo error.

The more the play the greater the wear, the idea being the rate wear is recorded and when reachs a set limit depending on material you plan for change the next time the bearings/shaft is drawn. 0.2mm on a 25mm shaft is the absolute max I let my bearings get too otherwise you might find the shaft gets damaged in way of the bearing.

Brian

Brian

 

[NorthUp]

If you can rattle the shaft in the bearing by hand, imagine how much your engine will rattle it at a shaft speed of 1500rpm!
3mm play is too much for a 40mm shaft.

 

[TigaWave]

It depends on the bearing, different manufacturers run different clearances to start with.

We would say 3-5% but clearances are 0.5-0.6% on a new bearing.

 

[Medskipper]

Ive been boating 25 years or more and its always been said that if you can move the shaft in the bearing by grabbing the prop and shaking it, then the cutless needs changing! in other words you should not be able to move it by hand at all.

Barry