Cutlass bearing clearance

[rajjes]

Would you consider 1/4" clearance between the cutlass bearing and the prop shaft anode sufficient for adequate water circulation in the bearing?

Setup is a 1" shaft, 2 blade prop behind a long keel.

 

[john_morris_uk]

The short answer is no. Can't you move the anode back a bit further? If you really can't then be prepared for more wear or problems with the cutlass bearing. Of course you might get away with it, but my bones say that its too close.

 

[LadyInBed]

I wonder! If a rope cutter is installed then it is up tight against the cutlass bearing.
So 1/4 inch would allow plenty of space for hydrostatic pressures to act.

 

[eyehavit]

Resilient mounted engines may need as much as 9mm for shaft fwd movement, PLUS a minimum of 2mm for water to exit.
You may be able to determine the distance by looking at the shaft. Normally there is a short distance of polished shaft protruding aft of the bearing.

 

[vyv_cox]

Here's mine.

Anode to P-bracket looks like about 1/4 inch or maybe slightly more, P-bracket to Stripper was 6 mm (1/4 inch) when set up according to instructions. The cutless bearing has been replaced once in my 11 years of ownership, so no problems there.

 

[boatmike]

Yes provided that the distance is maintained with your gearbox in both forward and reverse. The bearing actually "pumps" water through rather than relying on the forward motion of the boat so I disagree with the poster who said no. The short answer is yes!

 

[rogerthebodger]

[ QUOTE ]
The bearing actually "pumps" water through rather than relying on the forward motion of the boat

[/ QUOTE ]

Can you pls explain how this works

 

[eyehavit]

[ QUOTE ]

The bearing actually "pumps" water through rather than relying on the forward motion of the boat


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Can you pls explain how this works

[/ QUOTE ]

No, of course a bearing with longitudinal grooves can not pump water. Only a bearing with spiral grooves can move lubricating fluid in a given direction and there are very few of those used for water lubricated bearings.

I think the poster was referring to the small assistance provided by a rotating flange-like object such as a prop hub, or alternatively a zinc anode or rope cutter component rotating in front and in concert with the shaft. A weak centrifuge is generated inducing water to be flung radially away from the shaft in turn inducing water to be drawn through the bearing. The closer the hub gets to the bearing, and the closer to sealing the exit altogether, the more important is the centrifuge action.
With a water lubricated bearing, it is surprising how close a hub can get to the bearing yet the bearing still receive adequate water lubrication.
Of course for bracket mounted bearings once a boat is underway, water lubrication is directional and pressurised and greatly assists and overides any centrifuge effect of a rotating hub.

My main concern and what I was alluding to earlier is IF the axial movement is mis-calculated with an error on the low side, the hub ends up grinding into the bracket. Not smart imo.
Yes, for some boats 6mm gap is OK and yes for some boats, a 6mm gap is completely inadequate and will result in the zinc anode or ropecutter pranging into the rear of the bracket.
What seems to work as a general rule of thumb for determining a minimum gap is 9mm + 2mm for water exit.

Hope that helps.