Phenolic, brass, nylon?

[Mudhook]

I've just removed my cutless bearing for the first time. Searching around the internet I see brass shell replacements, and "phenolic". Anyone know the difference and what the pros/cons are.

A worn cutless bearing stowed away in the toolbox is rubber, but the one I've just removed appears to be of solid nylon/delrin or similar. Better? Worse? Obsolete? Does anyone know?

Finally, the bronze bearing housing has little apertures in its forward flange, with three small (1/8-inch) holes each side leading back towards the bearing itself. Does anyone know what these are for.

Thanks for any info.

Regards, Mudhook.

 

[Clyde_Wanderer]

Cant advice on best replacement cutlas, but the holes are to allow water in to the running surfaces, as they will be water lubricated, whatever the material.
I would be under the impression that the Phenolic would be the quitest and smoothest, but maybe not the longest lasting, and would probably be the more tolerant of sand grit etc.

 

[Tranona]

Not sure there is any substantive difference between phenolic or brass shells, just different manufacturers. Some say phenolic are easier to remove as they can be broken up - useful if you can't press the old one out.

 

[isandell]

I am not aware of Delrin or nylon-bodied bearings. Nylon would be a bad idea anyway due to expansion caused by water absorption.

When I replaced by bearing, I used phenolic on the grounds that the bearing is a bit tricky to remove and it's fair easy to cut a phenolic one.

Ian

 

[scottie]

sounds more like a stuart bearing
contact fairwaysmarine

 

[TigaWave]

If it is a solid bearing, it could be a fully composite bearing, definitely better, certainly not obsolete (these are replacing traditional rubber bearings in a number of vessels)

But you can normally (assuming the stern tube is bronze) replace the bearing with fully composite or rubber material in a phenolic or bronze carrier. Some boats (those with Aluminium stern tubes) will want non metallic bearing carriers, for corrosion reasons.

As others have mentioned nylon or other plastic materials for bearings suffer from water absorption issues, they also loose their mechanical properties with increasing heat.

I hope that helps.

 

[robscov]

The internals are the same for phenolic as brass, but you have to allow for the fact that phenolic expands slightly in water so don't clamp it quite as tight as a brass one. If the bearing is meant to protrude from stern fitting clamp I'd go for a brass one as you can get a good hold of it when to need to change it. If its a flush fit I'd go for the phenolic as it will be much easier to remove with a hacksaw!

Either way, don't whatever you do get any grease on the nitrile rubber interior of the bearing as it destroys it. If you must lubricate the shaft on re-fitting use soapy water.

All the best

 

[rogerthebodger]

The only material I would use for a cutless bearing is vesconite

see www,vesconite.com

 

[isandell]

So where do you get a vesconite cutlass bearing for a yacht?

Ian

 

[rogerthebodger]

Not knowing where you are in the world. Try a request for quote in their web site.

If you are in the UK try phoning
0800 731 9745.

I you speak to then nicely and you only need a small amount they mat sen you a free sample but don't tell everyone

 

[srp]

I second Vesconite - virtually nil expansion in water, very tolerant of adverse operating environment, and lots of good technical info on their website with regard to machining, tolerances etc. Get hold of a piece and take it to a local engineering machine shop with all the machining instructions from Vesconite.