How much cutlass bearing play is OK?

[Northeaster]

Hi Folks,

I replaced my cutlass bearing last year, as there was alot of play in it, while the prop shaft was still attached to the tranny coupler. Seemed to work fine all summer / no excessive vibrations.

Although the bearing is only 1 year old, I took a look at it, as the engine / tranny is out anyway, and the prop is off too. There is no play in the bearing if I lift up on the shaft in the front, and back of the strut at the same time.

However, as the shaft is NOT connected to the tranny right now, and it is about 3 feet long, being suspended by a strut that is only 5 inches long - there is some play in it, if I move either end of the shaft up / down.

The rubber inside looks good, but there does seem to be more scoring of the shaft, than last year - But, I may not have noticed it last year!

The engine mounts were worn some, and may have caused some misalignment.

Not looking for extra work, but if there is more play than there should be, I would rather replace it now - even though it's only 1 year old - maybe 50 - 80 hours of motoring!

Advice?

[senormechanico]

If there's no play when the transmission is connected, I wouldn't worry about it.

Steve B.

[Sandero]

Mine is hard to measure but it feels less than 1/16". It's fairly new and seems to do the job, but it definitely has a small bit of play.

[Alan Wheeler]

Yes it needs a little play so as water can lubricate the bearing. If you move it, you will feel it move slightly. That is normal. If it is really sloppy, like over the 1/16" as Defjef describes, then you may need to take a closer look.
Ensure your Prop is balanced and that there are no dings in the blade edges. Also ensure the leading edges are not too sharp. They need to be blunt and rounded. Otherwise they cause cavitation in such a way that it feels like a serious vibration. This vibration will wear away at the bearing.

[Celestialsailor]

The water does not lubricate the bearing by it's loosness. There are linear serations along the length of the cutless bearing that does this. A 1/16 or .062" play is excessive. When new, it should be a light slip fit. Either the bearing is worn out or the shaft is worn in the cutless area.

[Alan Wheeler]

OK, that's interesting. Mine doesn't have the slots along it. And yes I have seen some that have now you mention it. At least with mine, the wear has never increased in the five years I have been inspecting it. Each time I get the Guy in the yard to take a look and every time he has said, yep that's OK. Maybe 1/16th" is a little excessive in my guesstimate. What is that in mm. I would say in the region of 0.5mm would be the play for mine.

[Celestialsailor]

Maybe the bearings without the serrations use a different concept...Interesting. I wonder if the design you have helps for a longer life

[GordMay]

Originally Posted by Celestialsailor

The water does not lubricate the bearing by it's loosness. There are linear serations along the length of the cutless bearing that does this. A 1/16 or .062" play is excessive. When new, it should be a light slip fit. Either the bearing is worn out or the shaft is worn in the cutless area.

Exactly.
There should be no appreciable "play" in the Shaft - Bearing fit.

Pictured is a Johnson "Duramax" bearing.

[Northeaster]

Thanks for all of the advice. The play I am seeing may just be the rubber compressing a bit, as I try to move either end of the shaft up or down.
As mentioned, if I try to move both ends up, or down, at the same time, there is no play.

Senor M - Yes, I would like to see if there is any play while connected - but I don't want to put the engine / trannie back in, find out there is too much play, then have the engine in the way of getting the shaft out.
The shaft will come out to the stern, but the strut is only a bit offset of the skeg, so you have to temporairily bend the strut, so the shaft will pass by the skeg. Did this last year with some help, and may have bent the strut slightly - took alot of force to twist the stut enoough! It is bronze.

I may temporairily fasten a 2x4 across, where the trannie coupler would be, with a 1" hole in the middle, to place the shaft end. Then I could see if I have less play, once "attached"!

Thanks again!

[GordMay]

ABYC P-6 PROPELLER SHAFTING SYSTEMS
For Strut Bearing Tolerances, see Table V (page 6) at:
https://www.abycinc.org/committees/P-06.pdf

[pmeyer]

With less than 100 hours on a new cutlass bearing, I doubt there is much wear, unless the engine was badly misaligned. If you can grab both ends of the shaft and move it up and down and side to side with little to no play, then I wouldn't worry. Also, with the shaft out you can do a visual check of the bearing for uneven wear.

Paul M
New Brunswick Canada

[Northeaster]

Gord - Thanks for the link! Was just up in Thunder Bay last week for work. Hope that ice melts for you soon!! I was there around this time / end of April, last year, and there were a couple of boats in.

PMeyer - Thanks! I do agree with you, and think that it is fine. There is little / no play, when I move both ends up, down, or sideways, at the same time! I think the play I get, when I move one end up, the other down, is just the rubber compressing a bit, at each end of the bearing!

Like i said before - not looking for extra work, but I would hate to miss the opportunity to change something, now that it is easy!

[4HMainer]

Useful table Gord, but it doesn't cater for the ever increasing use of clearance fit cutless bearings. The new approach especially for composite cutless bearings is to have them finished as a clearance fit, bedding them on epoxy. There are advantages to this approach, the main one is that you get to see if the shaft and bearings are aligned. If they are, you can spin the bearing in the holder with the shaft installed (supported), then just coat in epoxy and slide into place.

[mbu745]

I bought a Moss cutlass bearing in 2008, which had plenty of play when installed; it seemed to me not right. When contacted the seller, everything would be OK after a while in the water. Eight months later I had to take the boat out again to replace the cutlass. The shaft was rattling in the bearing with exactly the same play like new. The seller was furious when contacted; with a lot of big words he told me this was just no possible. Perfect service from this people, I guess the bearing was not a 1 ¼ inch witch I ordered, but 1 5/16. A cutlass bearing with rubber inside shouldn’t have any play when installed. I still believe Moss bearings are a good deal.

[bigpuff]

if the water is muddy or thers been sand or the like b eing kicked up(run aground)it dosent take long for a cutless bearing to get chewed out,just one other thing a beneteua is in desimal not in inches