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cutlass bearing

5K views 14 replies 13 participants last post by  Ritchard 
#1 · (Edited)
I am beginning to think my cutlass bearing is worn. There is a little play in the shaft-not sure how much. Is there an acceptable standard for the amount of play? Shaft is one inch dia.

Is that a special bearing or can I go to a bearing supplier and get a standard bronze bearing if I need to replace it?
 
#3 ·
You need to know 3 measurements. ID, OD and length.

You should also double check these specs to the OEM specs as someone may have fiddled with the strut like they did on my boat. I found the strut to be over-bored probably because a PO had damaged it during removal. Luckily my strut is a bolt on and very easy to replace.
 
#4 ·
I've just removed mine - I discovered it was worn when we started work on the shaft log - Once we got into the project we decided to remove the shaft, which then needed to go to the machine shop to be dressed up (some wear grooves had formed over time at the cutlass and at the shaft log). There are a host of places to get the new bearing - I ordered mine through JD but only because I had other stuff to get.....here is a link to a catalog that lists not only the bearings, but replacement struts, and shaft log parts - buckalgonquin dot com

If the boat is on the hard, it might be good to go right back to the engine - we discovered the wear at the bearing was caused by the engine shifting over time - if we had stopped at the bearing, it would have failed prematurely because the engine was not aligned correctly (it actually was shifting due to some 'softness' in the stringers it was bolted to, but that's another thread for another day!)
 
#5 ·
When hauled, you should not be able to move the shaft up, down, side to side, or any combination thereof. However, you should be able to rotate the shaft along its axis by hand.
 
#8 ·
The cutlass bearing is a special bearing- often bronze lined with a rubber liner having grooves cut in to allow water to lube and cool it. There are other materials too however,such as fiberglass with a liner.
They usually have some wear after they've been in use for a while. It should not be too sloppy. The rule of thumb I use is a maximum 1/16 inch of radial play per inch of shaft diameter. Thus if yours at 1" diameter moves up to 1/16" radially it's still OK. Replace it once its over that 1/16" dimension. Just be sure your shaft isn't worn as well and contributing to the radial play.
 
#11 ·
Some comments on cutless replacement. It can be done without removal of the shaft by using a proper puller. But the best way is to remove the shaft. The only proper way to remove the shaft is by pushing it out of the coupling. This can be done by using a spacer (1/2 in socket works great) and some longer bolts using the engine flange to push out the shaft from the shaft flange. With the shaft out it can be properly inspected and cutless bearing is more easily installed. If a boat yard is going to do the work it is important to ASK them how they intend to remove the shaft. It they say they use a slide hammer tell them you will do it yourself. A slide hammer can damage the seal at the rear of the transmission. If you don't remove the shaft you could have calcium deposits on the shaft that will prematurely wear out the new bearing.

Gene
 
#12 ·
In answer to a few comments above, from the perspective of a bearing supplier.

Cutlass and cutless have become generic names for water lubricated rubber bearings (they are rubber bearngs as the bearing surface is rubber)

As the rubber needs support they often come in a carrier which can be bronze or composite, although some vessels use a rubber insert into the grp stern tube.

There are also other types of material for marine shaft bearings which have replaced and in some cases (Maritex) improved over rubber as a bearing surface. Many years of development have gone into new materials to improve on the performance of rubber.

These composite phenolic bearings are rarely a press fit as the manufacturers prefer a clearance fit bedded on epoxy which retains the ID, as there is no bore closure from the press fit option.

Clearances are different for different materials as they have widely differing thermal and moisture expansion rates. Each manufacturer has set clearances they work to.

So as an example...
a composite Maritex bearing for a 2" shaft in a 3" carrier
Running clearance new 0.24mm or just under 10 thou
Change bearing when radial displacement approaches 1.27mm
 
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