cutlass bearing install and shaft prep questions

[Muaddib1116]

I've pulled my prop shaft and the two cutlass bearings, one in the strut and one in the stern tube.

Unfortunately, I scored into the fiberglass with the reciprocating saw when I was cutting through the stern tube bearing. I don't think it's a structural problem, and I'm planning to fill it with thickened epoxy.

What I'm wondering, is what type of prep do I need to do to the strut tube and stern tube? There is some gunk that I'd like to clean out, but obviously I don't want to alter the ID or make it out of round.

Likewise, I want to clean the prop shaft in the areas around the bearing surface sections. What finish should I look to achieve? Mirror polish? or will a brushed finish do?

Thanks.

[tkeithlu]

Just for future reference, it's "Cutless," a brand name.

The cut in the fiberglass may need a patch or may be fine with epoxy as you suggest, depending on depth and the stresses at that location.

Clean out any gunk, but that's all for the stern tubes. If you have the shaft out, take a look at the surface of the shaft where it contacts the bearings. The goal here is that it be smooth and round, such that you get minimal wear in the soft part of the bearing. Very fine (1000, 2000 or so) sandpaper from an automobile parts store or Amazon will do that job. If you want to be really Type A about it, make the last sanding around the shaft rather than parallel to it.

Overall, my impression is that you may be over thinking this. Unless your bearings are being prematurely chewed up by your shaft, inserting new bearings and reassembly will be OK.

Good luck with it.

[Muaddib1116]

Thanks, it's the first time I've done this. I went deeper into the fiberglass than I wanted to, but obviously I would have preferred to somehow not touch it at all.

I wasn't sure if you're supposed to wax or grease the bearings to get then in, or conversely bed them in with some sort of sealant. I'm guessing it's more of a press fit with clean surfaces?

I'll use my best judgement on the shaft. I'll go for as fine a finish as I can get while still cleaning it.

[SailingHarmonie]

On the prop shaft:

Assuming you are reusing the old shaft, and assuming you are changing the cutless bearings before they scored the shaft, They should take very little cleaning. After all, they were rubbing on the old bearings, yes? The current finish on the shaft where it is in the bearings is likely smoother than a wire brush, and rougher than a mirror polish. No reason to change it.

Just in case you (or anybody else!) doesn't know this, NEVER use a steel wire brush on a piece of stainless--of any kind. It will leave small bits of steel imbedded in the surface and they will act as loci for serious corrosion.

[tkeithlu]

That's a good reminder. If you don't already have one, here's a brass cup brush for your grinder:

https://www.amazon.com/Makita-Piece-...s%2C147&sr=8-1

[Putt-Putt]

I have to agree with SH. about never using a steel wire brush on Stainless unless you want to make a real mess of it.

There are quite good nylon bristle cup and round brushes that are fit for stainless as long as you use them only for stainless. Buy a second set for use on all other materials.

Why theithlu linked to a Cup Brush that is constructed from 0.012" tempered carbon steel wired (like most cheap brushes) that is "brass coated" escapes me, when you consider the instructions in the link say "apply gentle perpendicular pressure ensuring full contact of the wire tips (that would be the carbon steel wire tips) only."

Weiler makes some reasonable Brass and Bronze brushes but you're going to pay 4 or 5 times the cost of the Brass coated steel brushes.

I'd still use nylon.

[tkeithlu]

I'm terribly sorry, and thank you, Putt-Putt, for catching the fact that that brush is brass plated, not brass. Yes, there is a cost issue - here's a truly bronze brush, and it's 3 to 4 times the price:

https://www.zoro.com/weiler-single-r...commended=true

Brass brushes for lower RPM use (in a drill, not a grinder) are much cheaper and easy to find, but then you don't get the speed of a grinder.