What does a Cutlass bearing look like?

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DickB

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I have a saildrive so this is purely acedemic interest but my friend has a 36 Bene with a traditional prop shaft. It vibrates a lot at certain revs (rattles) and I thought it might be the cutlass bearing, but I would like to see an exploded diagram of the thing and the different seals. The actual model of yacht I am not too sure but it is vintage -98 centre cockpit 36ft. Any ideas anyone? (It does not have a grease stuffing box as far as I can see...)

thanks
 
Illustration here.
These fit in to the P bracket just ahead of the propeller, and a small amount of play seems normal. If there is bad vibration then it might be caused because the propeller is out of balance or the shaft slightly bent. When the revolutions coincide with the natural vibration frequency of an out of balance shaft and prop. then the vibration can be really bad, with things much more comfortable at higher or lower speeds. Another source of speed related vibration is over soft engine mounts. Conversely, mountings that are too rigid can allow engine vibrations to transfer to the hull structure.
 
I believe that Beneteau and many french built yachts use a more inferior cutlass bearing which is made entirely of rubber( cheap) rather than the more traditional bronze tube with internal rubber sleeve. the rubber only type wear much more quickly and are best replaced. I own a dehler which, although german built was bought from a french owner who had installed the inferior rubber type. i have changed it to the traditional bronze/rubber but had to have the stock item lathe turned to take a thou or so off to fit correctly. the difference was noticed immediately
 
If not bearing ( And I guess you would have to lift the boat out to check the play) it could be something like a loose shaft anode. They can make a heck of a racket, especially if they start sliding up and down the shaft.
 
For the pedantic amongst us, it actually spelled 'cutless' bearing compounded from the two words cut & less. That's exactly what the bearing did when someone discovered that hard wearing lignum vitae wood (the tree of life) was used as the bearing which 'cut less' into the shaft than a plain metal bearing....apparently!
 
I think I'd let the boat dry out somewhere and get out and get under and have a decko! Maybe the prop is damaged or has got the wife's (girlfriend's) underwear tangled up on itl (Or rope or something more genteel.)
 
Thansk for all the advice. I know he is getting the yacht lifted in Feb and we can check it out. Lots of very useful information... It seem bizarre that a bearing surface is rubber!!! I would have thought it would wear out very quickly. Anyway thanks again for all the advice...
 
Not been mentioned that the rubber is hexagonal or similar, not round, (inside)and is water lubricated. Mine was replaced in 1996 and has done about 10k hours. They come in stock sizes, imperial, and usually need to be turned down to size.
 
what a load of b*****s, the cutlass bearing is actually made by volvo penta, it costs about £15 and is an elegant engineering solution. it has nothing to do with p brackets etc. it is a rubber bushing which fits in a figlass moulding that exits from the rear of the boat. rubber bushes running submerged in water are an almost perfect medium. it takes about 15 minutes to change. take the prop off, undo 2 plastic screws, gently lever it out with a large screw driver, grease the new one, push it in, replace the screws and prop and thats it. inexpensive engineering at its best!! if the shaft is rattling and rumbling check the alignment of the engine before blameing the engineering.
 
I do believe that your bearings may need a little lubrication.
Whilst volvo may make such bearings and they may be engineered to perfection it is more common for cutlass bearings to be located within a P bracket, rather than from an exit " at the rear of the boat". I am also confused as to " rubber bushes <u>running</u> under water" cutlass bearings shouldn't run anywhere. Finally if Dick B can obtain a cutlass bearing for a 36 foot Benetau for £15 then I'd love to have him ,or you source my spares!
 
if you dont know what you are talking about dont comment. benes and most of the modern boats have the prop shaft running in a tube that exits the "back of the boat" thru a moulding that forms a minature "keel"
in the exit of that tube they fit the rubber bush, they dont have a p bracket!!!! all engineers know that water is a good lubricant as long as there is enough of it. all you have to do if you want a genuine VP cutlass bearing is call Ancasta and ask for a 25mm cutlass bearing for a bene!! thats where i bought mine, have you bought a cutlass bearing for a bene? from your comments i think not!
i have been in engineering all my life and have changed these bushes in my bene so i know what i am talking about!!
shoot from the hip, generalise and you only end up making your self look foolish
Stu
 
yes but that is not what they fit in benes, the bearing is a small rubber bush shaped like a top hat with the rim acting as a flange to locate the bush in a blind moulding. two plastic screws hold it in place. the ones you have found fit in "true" p brackets.
stu
 
read the posts, he asked what it loooked like for a bene 36 foot centre cockpit!!, i told the forum what it looks like, specifically for a bene, i also reacted cause someone shot from the hip and started talking about generic p brackets, benes dont have p brackets as such in the latest boats and then they started on about it being a cheap way of doing it, it is a cost effective and elegant engineering solution.
a bene cutlass bearing looks like what i described.
stu
 
Whilst i may have been wrong in assuming that a "vintage "benetau '98 centre cockpit with a "traditional " prop shaft had a shaft support set up with "P " bracket, I do believe that the information which i gave is correct and results from experience changing 8 cutlass (cutless?) bearings on various craft (albeit all with "P" brackets) and having discussed the various virtues of rubber/ bronze /rubber with several marine engineers with many years experience. It is however a pleasure to communicate with the first person on earth "who has been an engineer <u>all</u> <span style="color:red"> </span> his life" what a child prodigy Stu must have been!
It is also rewarding to note that the thanks of DickB to forumites input arrived prior to Stu's unnecessary diatribe.
I suggest that anger management classes may be in order or perhaps a course of flower arranging
 
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