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Old 05-02-2013, 05:25   #1
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Cutless bearing shell material

I am replacing my cutless bearing. The chandlery has the Johnson bearings in both composite and brass shells, the same sizes and about the same price. I didn't see anything listed about relative advantages/disadvantages of the shell material on their website or in forum searches.

Anyone have an opinion as to if there is an advantage going one way or the other?
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Old 05-02-2013, 05:58   #2
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Re: Cutless bearing shell material

I am not sure brass goes with alloys. I would take resin for an alloy boat. Our boat is grp and so we replaced brass with brass.

BTW if you have plenty of difficulty removing the old one, you may opt for resin - brass was very difficult to cut the shell and dig the old thing out of the tube.

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Old 05-02-2013, 06:31   #3
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Re: Cutless bearing shell material

I can't use bronze cutlass bearing casings on my aluminum boat.

It is also going to be easier to remove a fiberglass bearing casing over bronze because quite often to remove them you have to cut them with a Sawzall lengthwise which allows them to bend to a slightly smaller diameter which makes them easier to remove.
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Old 05-02-2013, 06:34   #4
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Re: Cutless bearing shell material

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Originally Posted by barnakiel View Post
I am not sure brass goes with alloys. I would take resin for an alloy boat. Our boat is grp and so we replaced brass with brass.

BTW if you have plenty of difficulty removing the old one, you may opt for resin - brass was very difficult to cut the shell and dig the old thing out of the tube.

b.
Blue's outer bearing pushes up flush in the log, which always made removal difficult. I now buy the next outer shell size bigger, and have the it machined to size except for the last 3/4". push it in against the shoulder, and next time out, grip it with a Stilson. Easy change.
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Old 05-02-2013, 14:43   #5
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Re: Cutless bearing shell material

I like Blue Stocking's idea! I know the stock lengths are longer than the existing bearing, perhaps I can do this also.

Curioser and curioser, although Duramax only lists one OD for their 40mm shaft bearings (and one length), the chandlery has two different ones on the shelf: 40mmx2.12"x160mm and the size listed on the Johnson spec list, 40x55mmx160mm long. I'm wondering if the 2.12" one was turned down and then returned to the store.

The existing composite bearing was too small, and easily removed with lots of slop. It appears that perhaps the previous install it was supposed to be bed in epoxy, but the only thing keeping it in were the setscrews. Once I get the shaft out, I will clean up the stern tube and measure for the cutless.
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Old 05-02-2013, 14:58   #6
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Re: Cutless bearing shell material

+2 for Blue stocking's idea. I made a custom stern bearing housing for my boat to take a johnson cutlass bearing and by design 1/4 inch or so hangs out the end so that it can be pulled with stilsons at replacement time.

As for composite vs brass shells, my understanding is that composite is best used where the bearing will be epoxied into place or where the anodic index of the housing would be too great if a brass shell was used. Otherwise brass is best when press fitted and/or held in place with grub screws.
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Old 05-02-2013, 15:24   #7
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Re: Cutless bearing shell material

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(...) As for composite vs brass shells, my understanding is that composite is best used where the bearing will be epoxied into place (...)
They are not normally glued in. The fit is tight and a limiting screw is used.

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Old 05-02-2013, 15:41   #8
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Re: Cutless bearing shell material

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Originally Posted by barnakiel View Post
They are not normally glued in. The fit is tight and a limiting screw is used.

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When I was making my custom stern bearing housing I had the options of epoxy fibreglass construction or machined bronze. Had I used fibreglass the advice I received was to use a specialist low melting temperature epoxy to glue a composite bearing in place otherwise with the bronze housing to use a conventional brass shelled bearing with interference fit and two locking screws. Ultimately I opted for the latter.
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Old 05-02-2013, 16:04   #9
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Re: Cutless bearing shell material

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Originally Posted by Reefmagnet View Post
When I was making my custom stern bearing housing I had the options of epoxy fibreglass construction or machined bronze. Had I used fibreglass the advice I received was to use a specialist low melting temperature epoxy to glue a composite bearing in place otherwise with the bronze housing to use a conventional brass shelled bearing with interference fit and two locking screws. Ultimately I opted for the latter.
Doh.

We learn something new everyday! Low melting temperature epoxy glue - off I go to do some study!

THX for sharing.

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Old 05-02-2013, 17:07   #10
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Re: Cutless bearing shell material

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Originally Posted by barnakiel View Post
Doh.

We learn something new everyday! Low melting temperature epoxy glue - off I go to do some study!

THX for sharing.

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I think this is the kind of epoxy recommended from memory. My memory aint what it used to be but the 60 deg C melting/softening point rings a bell.

http://www.dawex.cz/userFiles/techni...ldite-2011.pdf
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Old 06-02-2013, 04:08   #11
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Re: Cutless bearing shell material

I had seen the other threads about the phenolic bearings and the low temp epoxy, but it looks like the consensus is that brass is the way to go if you have a fiberglass hull boat.

Anyone ever try icing the bearing/heating the stern tube ala shrink fit to make it easier to press into place?
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Old 08-02-2013, 09:27   #12
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I left my cutlass bearing in the freezer overnight, packed it in ice for the trip to the marina and slipped it 75% in. A few taps with a lump hammer and block of wood sent it home.
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Old 20-02-2013, 18:10   #13
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Re: Cutless bearing shell material

Had to have the stock brass bearing OD turned down, but it fit great after a night in the freezer, just a tap as twinboat said! There was a lip preventing it from being pushed further into the stern tube, but instead of having it cut off (almost lost out on that as the machinist was approaching the lathe with a hacksaw!) I left it proud as Blue Stocking mentioned so hopefully next time I can pull the bearing without pulling the shaft. Both OD and ID fit so much better now, I can't wait to get it back in the water! Thanks, everyone!
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Old 08-04-2013, 02:03   #14
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Re: Cutless bearing shell material

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Originally Posted by David M View Post
I can't use bronze cutlass bearing casings on my aluminum boat.

It is also going to be easier to remove a fiberglass bearing casing over bronze because quite often to remove them you have to cut them with a Sawzall lengthwise which allows them to bend to a slightly smaller diameter which makes them easier to remove.
I also have an aluminum boat and I am being given conflicting advice. Johnson makes a non metal cutless bearing with some sort of hard rubber on the inside diameter. The choice is to buy the material which is some sort of very expensive plastic and have it sized to fit at the local machine shop. Anyone with experience in this, please let me know your idea. I posted this question a few months ago but cannot find the thread.
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Old 08-04-2013, 23:03   #15
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Re: Cutless bearing shell material

Quote:
Originally Posted by David M View Post
I can't use bronze cutlass bearing casings on my aluminum boat.

It is also going to be easier to remove a fiberglass bearing casing over bronze because quite often to remove them you have to cut them with a Sawzall lengthwise which allows them to bend to a slightly smaller diameter which makes them easier to remove.
I also have an aluminum boat and I am now in Fort Lauderdale. I fly back to Thailand in two weeks where my boat is hauled out and I am looking for material to fabricate a new cutless bearing. Does anyone know where I can find the best material to make a new cutlass bearing in the US. Something the equivalent of Visconite or Maritex Aquarius?
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