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Old 05-13-2016, 05:13 AM   #1
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Cutlass Bearing - how tight a fit -new

Bought a Cutless bearing 1'' x 1 1/4" x 4" slipped it over the shaft and it was real sloppy, all along the shaft. - barely tighter than the old worn one. Thought, oh yeah the shaft's metric then. Went and bought a metric cutless - 25mm x 1 1/4" x 4" slipped it on and felt it tighten as I pushed it on and thought great - then it split length ways. WTF

So question is, how tight are NEW cutless bearings, I read somewhere that you need to freeze them first to get then on ?? If so, cutless bearings are quite tight fitted new.

Thinking - maybe I can just epoxy this into the housing and then slip it on the shaft and discount the fact it cracked/split. After all, the epoxy will fill the crack and it's nice and firm and glued into a housing and going nowhere.

P.S.The shaft is not worn as I moved the cutless along the shaft well beyond the point were it is mounted and felt no difference in resistance.
regards Brett
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Old 05-13-2016, 07:20 AM   #2
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Snug.....but not so tight it takes more than some twisting to slide it on.

Why it split is beyond me...but I have never used a composite one...was this one bronze bodied or composite?
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Old 05-13-2016, 08:18 AM   #3
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This link provides a good technical discussion. Allowable wear/clearance guideline is on page 20. For 1-2 inch shafts their number is .04".


http://www.duramaxmarine.com/pdf/Dem...StaveBroch.pdf


I wouldn't advise gluing the bearing into the hull.
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Old 05-13-2016, 08:40 AM   #4
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It should not be a sloppy fit. In fact it should be a press fit where freezing the bearing, if it's a metal one, can make it easier to slide it in.

Bearings can be floated and glued in place. Floating bearings need to be propery aligned each time they are changed. But yours is not that type.
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Old 05-13-2016, 08:56 AM   #5
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MaineSail to the rescue again: Replacing A Cutlass Bearing (Sleeve Bearing) Photo Gallery by Compass Marine How To at pbase.com

Here is a quote from the article
"There is tremendous force required to press a properly fitting bearing into a strut."
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Old 05-13-2016, 09:11 AM   #6
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Yes, tight into the strut or bearing carrier....but not onto the shaft and cause it to split.

Now I am not sure exactly what the issue is/was.
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Old 05-13-2016, 10:42 AM   #7
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Quote:
Originally Posted by bogranjac1 View Post
Bought a Cutless bearing 1'' x 1 1/4" x 4" slipped it over the shaft and it was real sloppy, all along the shaft. - barely tighter than the old worn one.
Was this first bearing in its housing when you slipped it over the shaft? It would be a tighter fit around the shaft if the bearing was inside the housing.
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Old 05-13-2016, 12:18 PM   #8
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Originally Posted by psneeld View Post
Yes, tight into the strut or bearing carrier....but not onto the shaft and cause it to split.

Now I am not sure exactly what the issue is/was.
Ooops... Right, sorry. Wrong problem.
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Old 05-13-2016, 01:37 PM   #9
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I'd measure the shaft. It sounds like you have a 1" shaft, and the 25mm bearing is .015" too small, causing it to split. The bearing must have clearance on the shaft to function, so there is no reason to make the composite body strong enough to resist the force of pushing a "too tight" bearing on the shaft. Once in place the body is supported by the bore of the stern tube or strut.

The composite body has to develop enough compression force in the stern tube to resist moving after pressing in place, and as it is more elastic than bronze it may compress significantly, making the excessive clearance you experienced with the 1" bearing diminish once pressed in place.

Good luck!
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Old 05-13-2016, 02:42 PM   #10
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Island Cessna, your right, got to be a 1" shaft. Maybe the composite material swells slightly on immersion with seawater and/or insertion in the cutless bearing housing and the impression I had of the new bearing being a bit sloppy was misguided.
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Old 05-13-2016, 07:27 PM   #11
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A new bearing should never be "tight" on the shaft. There always needs to be at least a slight gap for water to act as a lubricant between the two. The composite one that was snug going on and split was definitely too tight on the shaft.

Ken
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Old 05-13-2016, 07:41 PM   #12
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A new bearing should never be "tight" on the shaft. There always needs to be at least a slight gap for water to act as a lubricant between the two. The composite one that was snug going on and split was definitely too tight on the shaft.

Ken
Not exactly true. A new bearing will usually be snug on the shaft to the point that you most likely will need to lube the shaft with soap to get the shaft to slide down the bearings.

The bearing will break in pretty quickly and the space for the water to fill the gap will form pretty quickly as well. If it isn't already there.
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Old 05-13-2016, 08:07 PM   #13
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I put in Vesconite bearings. They are some kind of hard plastic.
I put them in 2006, so been 10 years. I hauled out in 2014, there was no wear. none at all.

They are also a lot less money than the bronze bushing with rubber lining.
I did get a crab pot line wrapped the shaft and it dug into the end of the vesconite bushing.

They pressed in after I put them in the freezer. I had taken off the struts, so I did this at the house.

https://www.google.com/search?q=Vesc...hrome&ie=UTF-8
When I ordered these, they came from South Africa by airmail.
they will also custom cut and machine vesconite if you wish
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Old 05-13-2016, 09:06 PM   #14
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When I set up my driveline, I bought a new 1 3/4" shaft and new cutlass brgs to fit. With brg in hand it would slip onto shaft with just a hint of clearance, maybe 0.005 to 0.010" guessing. There was a few thou interference in the struts, so the clearance tightened up a bit once pressed in. But still there was some clearance, once all lined up and installed it was an easy roll of the shaft by hand.

If that brg split, it either had a flaw or you beat the heck out of it getting it on.
Something seriously wrong.

Metric shaft 25mm is 0.984"
SAE shaft 1.000" is 25.4mm

16 thou different, more than typical cutlass brg clearance.
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Old 05-14-2016, 06:37 AM   #15
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Semi planning.............at no time did I mention "glueing the cutless into the hull"
Ski in N.C...................I merely pushed the bearing along the shaft I DID NOT "beat the hell out of it"
Although sometimes I feel like "beating my head" against a wall when posters can't read
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Old 05-14-2016, 06:52 AM   #16
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I understand that what split was the rubber bearing by itself, not the bushing or "housing" it sits in.

Splitting the bushing would take some beating and gluing it to the hull be a really bad idea.
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Old 05-14-2016, 07:00 AM   #17
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I am not sure that is correct either.....I think the composite around the actual bearing split.

And no I would not epoxy it in be a use if it didn't work....tough to fix with a new bearing.

I would try and return the bearing...even if I had to get another first and work the broken one out later.
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Old 05-14-2016, 07:19 AM   #18
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I would measure accurately the stern tube and shaft, get the correct bearing. Is the sterntube metal or composite? If metal get a metal sleeved bearing. drop in the freezer for a few hours, whip it out rub some washing up lquid on and tap it right in. Taking care to leave at least and inch free on the out side of the tube, to allow for removal of the bearing later in life. The photo appears to show that there may have been an external cutlass bearing at some time? How old is the boat? Composite bearings tend to be on smaller boats and more so sailboats of european extraction.
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Old 05-14-2016, 07:24 AM   #19
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Also is there any thread visible on the end of the stern tube? I believe I can see where the 2 bolt positions for the external cutlass where in the photos, and if there is thread there then it was set up for the external cutlass arrangement..Another factor is the inset in the deadwood, this was for the lip of the cutlass holder. How much shaft protrudes from the deadwood?
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