Another cutless bearing replacement question (or two!)

[leecea]

I am hoping to replace my cutless bearing this weekend using a Strut Pro, so the shaft has not been removed. I have two questions...

Q1:

I've read that refrigerating the bearing is normal practice to ease the install.

Since the ambient temp is about the same as a fridge, that may not be helpful. I wonder if using a heat gun to heat the p-bracket is a better idea.

Any thoughts on that?

Q2:

Should I apply any lubrication the inside and/or the outside of the bearing?

I've read that anything used on the inside should be water soluble so was thinking of Dawn dish liquid. But the boat will be sitting on the hard for another 2.5 months and even that could solidify and block water access.

Maybe just use water?

What do you suggest?

Thanks,
Andy

[leecea]

Oops - I had one more question...

I understand that I need to drill small indentations for the two small set screws (grub screws) that stop the bearing from rotating. I noticed that the existing bearing has holes that go right through the outer metal layer.

Should I drill right through the metal layer or is it better to try and just make a small "indentation" with the drill?

Thanks again.

[skipperpete]

Hi Andy, a dimple in the casing is used only to stop the grubscrew from going in too far, if you have pan headed, countersunk or hex headed screws of exactly the correct length the holes can be through drilled. In reality with an interference fit bronze housing , the screws are hardly necessary, Beneteau use a soft rubber shaft bearing that is a gentle hand push fit in the P bracket with a plastic locating screw into the rubber.... no housing at all and so far, I’ve never seen one of em come adrift so the interference fit bronze housing we mostly use is a bit overkill. Has anyone here on the forum ever had a cutless bearing come out of the stern tube or ....I have not ....BUT, I have however seen 3 instances where the rubber insert detached from the bronze casing and slid out to the propeller.

[Bowdrie]

I would add that in our little boats you should never have to freeze the bearing or heat the strut to install the bearing, nor should you be beating it in with a hammer.
With a good coat of anti-seize in the strut and on the bearing, it should go in only needing light to moderate effort, using a block of wood to rap the hammer against.
I have at times had to put a bearing on a mandrel in a drill press and use emery cloth to take a couple of thousands off of the brass shell.
Make sure the strut is nice and clean inside.

[lockie]

Easy to make up a tool using threaded rod and suitably-sized washers and nuts for a well-controlled and easy way to press it in.Cheers, Graeme

[leecea]

I'm using a Strut Pro, which I hope makes the process easier (first time using it).

[pcmm]

Originally Posted by Bowdrie

I would add that in our little boats you should never have to freeze the bearing or heat the strut to install the bearing, nor should you be beating it in with a hammer.
With a good coat of anti-seize in the strut and on the bearing, it should go in only needing light to moderate effort, using a block of wood to rap the hammer against.
I have at times had to put a bearing on a mandrel in a drill press and use emery cloth to take a couple of thousands off of the brass shell.
Make sure the strut is nice and clean inside.

Freezing the bearing is one of the installations methods recommended by Duramax/Johnson. Not sure why you think you should never freeze the bearing. Cutless bearings are an interference fit. Freezing the part (or heating the carrier) is how you fit an item that is interference fit. One of the two parts has to temporarily get bigger/smaller to be able to make the fit.

[Cheechako]

Good luck getting the old one out! That's usually the problem, even with the shaft out, much less with it in! In two instances I have had to saw it out a chunk at a time with a sawzall!

Should I apply any lubrication the inside and/or the outside of the bearing?

I've read that anything used on the inside should be water soluble so was thinking of Dawn dish liquid. But the boat will be sitting on the hard for another 2.5 months and even that could solidify and block water access.

It should slip right on the shaft, they are not tight. Nothing needed. I have not used anything on the outside, but I suppose you might if it's very tight, but I would try freezing it.

[Bowdrie]

Originally Posted by pcmm

Not sure why you think you should never freeze the bearing.

Don't read what ain't there.
What I said was is that you never should "have" to freeze a bearing.
Yes, they are an interference fit, but shouldn't be very much.
But I've only done perhaps a few dozen or so of Cutless bearings.

[Pete7]

Originally Posted by Cheechako

Good luck getting the old one out! That's usually the problem, even with the shaft out, much less with it in! In two instances I have had to saw it out a chunk at a time with a sawzall!

Twice I have had to get the hacksaw out and cut a 10mm wide strip in the old bearing before it would come out. A puller won't work as there is a lip at the front stopping anything getting a purchase to pull the bearing out. I have switched to a GRP bearing shell with the rubbing inside like a brass bearing.

I will know in a few years time if it was worth the effort.

I previously had a marine engineer fit a new bearing. He drilled the brass shell in place and put 3 little dents in the shaft with a burr. You can imagine what happened to the rubber insert and the shaft not only went round but in and out as you accelerate.

A year later the bearing was shot, so replaced it myself. Tried cleaning up the burr but despite being mirror polished it didn't work and £250 a new shaft went in.

The little grub screws will grip the brass shell, so I don't think you need to take a drill anywhere near it. Worth running an old flap wheel gently up and down the p bracket to clean out any corrosion before the new bearing goes in. Dish soap contains salt doesn't it? I would leave it clean smooth and dry. Never a problem gently tapping the new one in using a wooden block to stop any damage on the end.

Pete

[leecea]

I previously had a marine engineer fit a new bearing. He drilled the brass shell in place and put 3 little dents in the shaft with a burr. You can imagine what happened to the rubber insert and the shaft not only went round but in and out as you accelerate.

A year later the bearing was shot,

I wonder if this is my problem. I had a new shaft and bearing installed by the yard 2 years ago and when I hauled this year I noticed that the rubber part of the bearing was starting to protrude out of the bracket. Overall their work was a mess and required a couple of re-dos, and now I wonder if they damaged the new shaft in the way you describe. I guess I'll try to inspect the shaft when the bearing is out.

[pcmm]

Originally Posted by Bowdrie

Don't read what ain't there.
What I said was is that you never should "have" to freeze a bearing.
Yes, they are an interference fit, but shouldn't be very much.
But I've only done perhaps a few dozen or so of Cutless bearings.

I'd sure like to know how you get an interference fit item installed, without pounding it into place, or doing something to make one item slightly smaller to install... If you can install them with a bit of pressing by hand...that's not an interference fit.

I haven't installed a few dozen, but I do understand the physics. Shrink the bearing slightly so you can slide it in place (still usually takes some force) Once its back to normal temp its locked in place.

What you said was "you should never have to freeze the bearing or heat the strut to install the bearing, nor should you be beating it in with a hammer"

[nuku34]

Just a suggestion to the OP: I personally wouldn't use Allen hex head grub screws. There's too much chance of the hex recess getting striped out when its time to remove them. Then you are forced to drill out the grub screw, in the process destroying the female threads in the P bracket.
Rather, I'd use a normal machine screw with hex head and cut it to length so that the head ends up just proud of the P bracket surface. The added drag of the head is infinitesimal on a cruising boat.

[Toccata]

FWIW
I chose the non rubber bearing, locally referred to as a "rag type" looks like tufnol??
The local marine engineers are sceptical about the durability of the rubber type, particularly with any heat buildup.
Cleaned inside the P bracket with a flapper drum sander. Machined the O/D of the new bearing until it was a slightly loose fit in the P bracket.
Supported the shaft in the centre of the P bracket (by wedging it at the forward end with timber wedges agains the lead in fairing)
Check the bearing fit, now clear all round.
Slid the bearing along the shaft with a smear of epoxy glue on both surfaces.
Installed grub screw (as a "belt and braces" exercise) with no pressure on the bearing, into a predrilled indent in the bearing.
The shaft spins freely. This technique avoids any misalignment of the bearing possibly caused by misalignment of the P bracket. The bearing is totally true to the shaft. Note; of course the shaft needs to be correctly installed and aligned

[leecea]

Just a quick note to say that I did the replacement this afternoon. Removing the old bearing with the Strut Pro was easy, but mine is just a 1" shaft with a 1.25" outer diameter for the bearing, so small compared to bigger boats.

Pressing the new bearing in was harder. I did put it in ice/water for 20 mins. Trying to heat the strut with a hot air gun didn't seem like a great idea so I gave up. Ambient was around mid-40 F. I didn't use any lubricant.

Anyway... it's in. I'll see what it's like at next year's haul-out.