Plastic suitable for cutlass bearing please.

[mickshep]

Our boat is fitted with a Hydromarin hydraulic system driven by a 12hp diesel. The prop shaft runs inside a stainless steel tube that has what appears to be a large nylon looking bung in the outboard end, through which the shaft runs. This appears to be the cutlass bearing and is worn to the point that the shaft can be moved about 2mm from side to side, Firstly I am assuming that the 2mm of play is excessive, If so what plastic should I be looking for to have a new water lubricated 'Bung'/Cutlass machined up from, A supplier would be handy too, Cheers all, Mike,

 

[srp]

Vesconite - have used it for a couple of boats. UK supplier is:
Vesconite Sales Ltd
338 Billing Road East
Northampton
NN3 3LJ(Road Map)
Northamptonshire
Tel: 01604 231948
Fax: 01604 231948
The website www.vesconite.com has a wealth of information on a host of applications, including marine of course. They also have a very useful on-line calculator so whoever is machining it can make it fit perfectly.
The boat I've just sold had one fitted 7 years ago, and showed no measurable wear in that time. I've just machined one up for my new installation. Don't just use any old bit of plastic that comes your way - some of them swell alarmingly within just a few hours of immersion.

 

[beneteau_305_553]

Don't use nylon - it swells with moisture.

Polyethelene would be fine if the surface presure is low (what is the length of the bearing) or Acetal which is harder but may wear the shaft.

Start off with about 0.5 mm clearance.

 

[ccscott49]

Dont they make some cutlass bearings out of "phenol" not sure what it is.

 

[stevebirch2002]

I have made stern bearings for the Vega Association for the last 8 years. I have used an "Oil impregnated nylon". There are various trade marks such as "Oilon" and "Nyoil" Absorbtion is about 2% so this must be taken into account.

 

[TigaWave]

Composites have a few advantages over plastics for bearings but then I'm biased.

 

[neil_s]

This winter, I have replaced my worn white metal outboard bearing with nylon 66. I made allowance for the water absorption when machining to size. The bearing will be grease lubricated as before. I did try a rubber bearing for a season, but I found that the shaft tube was filling up with mud (I have a drying mooring).

Cheers! Neil

 

[mickshep]

Thanks all, plenty of food for thought, Mike.