Beneteau cutless bearing

[Sandy Stone]

Pardon me for posting this inquiry on the general board, but I thought a few more experts might see it.
I am replacing the cutless bearing on my new-to-me Beneteau 375 with a Volvo 2003 motor. After much wailing and gnashing of teeth, I have pulled the prop, separated the shaft coupling, driven the shaft out of the coupling and removed it, and removed the old cutless bearing. I just wish it was as easy to do as to write.
Now, I am ready to reassemble things and have found an anomaly. The new 1" ID x 1-1/2" OD bearing is loose on the shaft, but a tight sliding fit in the strut. Loose, as in I think the shaft might be 25mm instead of 1". No big surprise, it is a French boat. However, a standard 25mm ID bearing is 40mm OD, or something like 1-9/16". I don't see any way in the world that is going into the strut.
The shaft is not perfect, but I don't see it being worn down 1/32" of an inch or so, in fact I don't detect any kind of shoulder or ridge where it rode in the bearing. So, my question is: has anybody ever heard of a cutless bearing that has a metric ID and English OD? After going to all this trouble, I would hate to put a loose bearing back on the boat.

 

[RichH]

In all probability the bearing is a "Duramax" bearing and there should be a FOUR DIGIT alphanumeric 'stamping' on the OD of the bearing you removed. That 'alphanumeric code' will equate to the exact size requirement of the 'replacement' bearing. The alphanumeric stamp code sometimes is 'very faint' and may be 'smeared' by the removal - so look very carefully at the OD in bright white light to see it.

 

[bria46]

These folks have metric sizes. http://www.deepblueyachtsupply.com/series.aspx?id=2

 

[CYQK]

Sandy
My shaft size on my first 42 is 30mm check with Todd at Beneteau could explain why yours is loose

 

[Ron20324]

Go to the Beneteau Syselios parts web site. They would have the bearing and probably the size plus other parts you may well need sooner or later.

 

[DougM]

OK, you've got my curiosity. First 25mm is effectively the same as one inch (actually 25.4 mm). I suppose I would take a micrometer to the shaft and determine exactly what it does measure.

Second, since I was gping to do a prop change anyway this Spring, my plan was to change the cutlass bearing. I don't quite understand why you found it necessary to completely pull the prop shaft. I thought one could replace the cutlass bearing without removing the shaft at all on my 323. The bearing is in a skeg, not a strut, and it appears that it would just slide off the shaft. Please enlighten me.

 

[Sandy Stone]

25mm is close enough to 1" that when I measured my shaft I thought it was indeed 1". Especially since the OD of the cutless bearing is exactly 1-1/2", which would have made it a standard size. However, that .4mm (about 1/32") is enough to make the shaft noticeably loose inside the bearing, which is unacceptible to me considering the effort expended in disassemblng everything. My current plan is to get hold of a 25mm ID x 40mm OD bearing and have the OD turned down to 1-1/2" at a machine shop.
As far as what it would take to replace the cutless bearing on your boat, I can't comment because it is a different setup on a different boat. If you can change it without removing the shaft, more power to you.

 

[tommays]

Life in the marine world makes anything "slide off the shaft" a lottery winning kind of event

There is a fancy pusher you can buy and someone posted a very nice homemade pusher a while back

 

[RichH]

No! 25mm is not close enough to 1.00"

A cutless bearing is NOT measured 'loose' on a shaft, etc. The IMPORTANT 'final' measurement of the *Installed* bearing is what is 'important', here is a short explanation of why:

A cutless or any other 'plain bearing' is held in place by the *pressure* that the 'bore of the housing' bears down onto the outer diameter of the bearing. Such a bearing installation is called an INTERFERENCE FIT - the bearing OD is larger than the bore of the 'housing'.
Typical *standard* interference fit (just about ALL plain bearing, etc.) will be 0.001" per 1.00 inches of housing ID. The "FORCE" used to 'press' the bearing into the bore will create sufficient friction so that the bearing is held in place under normal expected operation. HERES THE IMPORTANT PART ---- when the bearing (with larger OD) is pressed into the ID of the SMALLER housing ....... the ID of the bearing becomes 'smaller' .... and that apparent 'shrinking' and the FINAL dimension of the INSTALLED bearing MUST have sufficient 'running clearance' between the bearing surfaces and the shaft. Typical 'running / installed' clearances are determined by the bearing manufacture .... usually requiring an 'installed in the housing' bearing to shaft clearance to be 'something to the order of' .... 0.001" to 0.005" (sloppy) 'clearance' PER INCH of shaft diameter --- this will result in a PROPER operating clearance so that the proper 'hydrodynamic film' of water is between the shaft and the bearing and prevents the bearing from 'cutting the shaft' (Cut-Less).
If you want a PROPER installation ... you need a micrometer. You need to either find the alphanumeric code embossed on the OD of the removed bearing ... and replace 'in-kind' ......... OR you need to use a micrometer and measure the UNINSTALLED OD of the bearing AND the Shaft diameter to the nearest 0.001" AND the ID of the 'housing' to the nearest 0.001" --- and then consult the bearing manufacturers data listing for the RECOMMENDED bearing to FIT. You dont call good old Charley at the parts counter of the boat builder to do this as shaft diameters change due to surface abrasion of the shaft operating inside the cutless ... unless you dont mind replacing the bearing much much sooner than that of a bearing that was properly sized, set and pressed.

The EASIEST (but not 'perfect') way to size the bearing is to obtain the embossed alpha-numeric code on the OD of the removed bearing, etc. .... otherwise, 'oil up the micrometers', and calculate the proper 'ID closure' of the bearing in the housing to determina a reasonable shaft to installed bearing clearance typically 0,001 - 0,003" per inch of shaft diameter.

 

[redhead78]

cutlass brg

Hi, Sandy,I under stand your grief. I also have a french boat,Jeanneau. When you say loose, how is it in relation to the way the old one fit. I had opposite last year, I replace everything, I was advised to switch to a 1" shaft. The shaft log OD is 40mm also. I used an all rubber bearing came wf boat, nice and snug in the tube. The old shaft was 25mm, slightly less than 1". I thought it was too tight but was advised by the yard it would be ok.I mean it was hard to turn a 16" prop by hand..I was afraid it would tear out that little set screw and spin in the shaft log. Turns out it was ok, after whole season its the same. Check out pics of old one....holy crap...Red

 

[Sandy Stone]

Redhead, 'loose' means I can wobble the shaft inside the new 1" ID bearing as if it was already worn out. No way. I haven't received the 25mm bearing yet to check it out.
RichH, unfortunately the old bearing did not survive the removal process. The new 1-1/2" OD bearing is what I would call a tight slip fit (there's a technical term!) in the strut. In other words, you can push it by hand roughly halfway into the strut, and would need a few light taps to get it the rest of the way in. Since the strut has 2 setscrews, I'm satified the bearing will not spin or come out. After what I went though removing the old one, I really don't want a press or interference fit on the new one.
While we're on the subject, when I put all this stuff back together, does anyone recommend some type of never-seize or corrosion inhibitor (Tef-Gel?) on either the cutless bearing OD or the end of the prop shaft where it goes into the coupling?

 

[RichH]

RichH, unfortunately the old bearing did not survive the removal process. The new 1-1/2" OD bearing is what I would call a tight slip fit (there's a technical term!) in the strut. In other words, you can push it by hand roughly halfway into the strut, and would need a few light taps to get it the rest of the way in. Since the strut has 2 setscrews, I'm satified the bearing will not spin or come out. After what I went though removing the old one, I really don't want a press or interference fit on the new one.
While we're on the subject, when I put all this stuff back together, does anyone recommend some type of never-seize or corrosion inhibitor (Tef-Gel?) on either the cutless bearing OD or the end of the prop shaft where it goes into the coupling?

NO NO NO NO NO NO
A plain bearing is held in place in the housing by the bearing being larger in size than the 'hole' that it fits into - the 'interference fit'. The SET-SCREWS are there ONLY to prevent the bearing from coming loose in the VERY remote possibility that the 'housing' becomes overheated (which increases its diameter and thus becomes 'loosened' with respect to the bearing) - a 'backup' restraint.
NO lubricants nor 'glues' are used when PRESSING bearings into a housing - DRY ONLY.
If you 'tap' the bearing into the housing, you will most probably permanently change the dimensions of the bearing.

You may use a corrosion inhibitor on couplers, etc. with NON-TAPERED (straight) geometry BUT these too are connected by INTERFERENCE geometries ... and the 'set screws' are there ONLY as a 'BACK-UP' if the friction provided by the INTERFERENCE FIT fails due to undue or unanticipated thermal changes.

 

[Maine Sail]

NO NO NO NO NO NO

DITTO, DITTO, DITTO !!!!!!

The only lube you may want is some dish soap or glycerin which washes out with water but that just prevents thin walled bearings from buckling under the pressure of insertion. They should also be pressed in not hit with a hammer. Thicker walled bearings should not require lube and only really tightly fitting thin walled ones may. MANY boats do not even have set screws. This is an interference bearing fit!! If you can push it in half way by hand the fit is wrong and you'll wind up in trouble...

This is what happens when a prop or coupling are fitting incorrectly. A cutlass (for Rich Cutless[SIZE=-1]®[/SIZE]) can have an equally bad outcome.

 

[tommays]

I don't know what is supposed to be in there but no metric size is close to 1-1/2 as a standard 25 x 40 mm would way to big

If you have to use the bearing some red loctite and it will never move

I repair plenty of machinery that requires the outer races to be installed this way and without heat its not coming out

 

[RichH]

If you have to use the bearing some red loctite and it will never move

Totally disagree if you have to use 'glue' to hold a plain bearing in its housing, the bearing is the WRONG size/dimensions and the bearing will never ever attain its 'installed' dimensions and intended/designed clearances.

 

[tommays]

Rich

Its a hunk of rubber vulcanized into a metal sleeve that might compress .001 in the strut which is installed badly much of the time

Then a shaft is going to pass through it to a motor 4' away and somebody is going to take there best WAG with a feeler gauge and line it up

I know my boat was sure a heck out of line for 40 years

 

[Sandy Stone]

I pretty much have to agree with Tommays on this one. I mean, it's a 25-year old boat and I'm doing the work myself. I can't believe that the the entire propulsion system is lined up to within a couple of thousandths of an inch, or that it ever was. I'm going to have the 25x40mm bearing turned down to fit in the 1-1/2" strut, with a clearance that will not require extraordinary tools or effort to install, or remove sometime in the future. In fact, the question about never-seize was aimed at later disassembly, not lubrication for installation.
I'm pretty confident that when I finally get though this, the boat will last to the next haulout without sinking, dropping the shaft or bearing, or seizing anything up. I would even go so far as to say that it will probably be in better shape than at least 3/4 of the boats in the water now.

 

[Witzend]

Totally disagree if you have to use 'glue' to hold a plain bearing in its housing, the bearing is the WRONG size/dimensions and the bearing will never ever attain its 'installed' dimensions and intended/designed clearances.

I drilled mine out to correct a serious alignment problem and floated the new bearing in with epoxy. This is how it's done on larger systems commercially. You want to change the bearing in the future just heat with a torch destroy the epoxy (making sure the top of the strut does not get too hot) and out it comes.

 

[gettinthere]

Hey MS, don't you have a supplier in India that can help with this?

 

[Maine Sail]

I'm going to have the 25x40mm bearing turned down to fit in the 1-1/2" strut, with a clearance that will not require extraordinary tools or effort to install, or remove sometime in the future. In fact, the question about never-seize was aimed at later disassembly, not lubrication for installation.

You've been given accurate information about the proper fit of these bearings so all I can say is cross your fingers and good luck. I've seen the results of sloppy cutlass bearing fits and it is not a pretty sight.