Another cutless bearing replacement question (or two!)

[pcmm]

Originally Posted by 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.

"freezing" the bearing really requires putting it in the freezer for a day or 2 before you need it. It still wont slip into place but you can press it in a bit easier.

[Bowdrie]

Originally Posted by Pete7

Never a problem gently tapping the new one in using a wooden block to stop any damage on the end.
Pete

Originally Posted by pcmm

I'd sure like to know how you get an interference fit item installed, without pounding it into place,

Yes, with the little shaft/bearing that the OP has, what "Pete7" said is what I was trying to say,
When the parts fit correctly there is no "pounding", (as you said,) or "beating" (as I said you shouldn't be doing).
There is a huge difference between a couple of thousands and several/many thousands on the little stuff that most of our smaller boats use.
It's the same on the machinery I've rebuilt.
An all-steel ball-bearing with .0015>.002 interference goes in/on with "tapping", (lighter blows,) one with .005 needs "pounding" or a press.
I know one thing, when you "pound/beat" in a Cutless it sure doesn't want to come out at changing time, and if it's one that you can't get behind it with a tool you're in for some real colorful language.
As an aside. For those of you that have a Cutless that goes into a "blind bore", (against a shoulder in the casting,) where you can't get a tool behind it, when you install the new one leave ~3/8ths > 1/2" sticking out of the housing.
Now you have something you can get your water-pump-pliers on to twist the bearing, and often you can change the bearing without pulling the shaft, (if it hasn't been installed with too heavy of force).
And it leaves a recess at the back of the bore to get a little pulling tool in if the shaft is out.
It'll make it SO much easier next time you need to remove/change it.

[skipperpete]

Originally Posted by pcmm

"freezing" the bearing really requires putting it in the freezer for a day or 2 before you need it. It still wont slip into place but you can press it in a bit easier.

I don’t know why this is true, but it seems to be. logically a piece of metal in a freezer should get as cold as the inside of the freezer fairly quickly but from my experience with replacing engine cylinder liners ( lots of em) it seems to be that liners soaked overnight go in better than ones that only got a 2 hour soak in the freezer before installation. I’d never try and freeze fit a cutlass with a bronze case and certainly never try and hammer one in. I have had cause to freeze Thordon shaft and rudder bearings, they’re one tricky bugger to install.
Here in Australia, there’s a protocol of chilling the beer overnight before a sunday BBQ, apparently a dedicated beer drinker can tell the difference….. not me though😎

[cottonsail]

Has anyone considered repairing a cutlass bearing? There are multiple slots in the bearing for water lubrication. What if a Teflon square piece was inserted into the open slots at 12, 4 and 8 o'clock positions? Of course, the Teflon would have to be precisely machined to fit. It's just a thought. I'm not too far from replacing my cutlass bearing. Starting to feel a slight vibration. To change mine requires removal of the entire powertrain and shaft. Again, just a thought.

[Bowdrie]

Originally Posted by cottonsail

What if a Teflon square piece was inserted into the open slots at 12, 4 and 8 o'clock positions? Of course, the Teflon would have to be precisely machined to fit.

To change mine requires removal of the entire powertrain and shaft. Again, just a thought.

First point, back in the pre WWII days William Atkin specified stern bearings made of Lignum Vitae for many of his powerboats.
They were just a simple block that was bored lengthwise for the shaft and bolted into/onto a bracket.
It makes a very good bearing with water lubrication.
I believe the US Navy still uses Lignum Vitae bearings on submarines.
I found a website a couple years ago of an outfit that was making them for the navy.
Second point, the designer of your boat should be put in the stocks, (so the townsfolk can throw tomatoes at him,) for such a design.

[skipperpete]

Ouch Bowdrie, you’re forcing me to reveal how young I’m not! I’ve installed the lignum vitae shaft bearings in the earlier part of my career, but not as a block though….. as dovetail staves that push into the sterntube and interlock around the propshaft. These days most large sterntubes are oil filled with a tank on the bulkhead to provide a pressure head. No more lignum vitae these days but thordon still produces the staves to the earlier pattern. They were replaceable from inside or outside the ship, had a threaded hole for the extracting tool and generally came out without too much huffing and puffing.

[capt jgw]

Make sure you get all the grub screws out of the strut or bearing carrier. There's almost always two per hole. On my twin screw cruiser some dumbass put three screws in one of the holes and I spent half a day with the Strut Pro trying to get the bearing out, and burned out the brushes in my electric impact wrench. I ended up pulling the strut off and didn't find the extra screw till I got it on the bench. I know I had removed two screws per hole, I counted them.

[Bowdrie]

Originally Posted by skipperpete

Ouch No more lignum vitae these days but thordon still produces the staves to the earlier pattern.

Lignum Vitae is alive and well for ship bearings.
Now they use it for parts of shaft seals too.
The William Atkin boats were smaller boats, a block of say ~4"X4"X6" long with a 1-1/2 bore thru it for the shaft.
Here are some, no other material is really any better.
https://maritime-executive.com/featu...or-shaft-seals

[plittle2005]

The best way to freeze press-fits is to pack in dry ice. Transmission bearing cups, taper-fit shaft hubs etc. are usually fit this way. The interference dimensions are matched to the available difference in temperature so the assembler can predict the initial slip fit.

Or...just pay the yard $2500 to do your twin screw replacements! You don't have to freeze the check!