Cutless Brn Wear

Ahoy All , my cutless bearning was causing abnormal noise on a recent long distance voyage.

After a haul out at my destination , my SS Aquamet shaft , upon removal looked like it was loaded with “gauling” at the bearning location .

I suspect the shaft loaded up with a calcium scale while siting idle at the dock for many months, then when underway and under power, that scale rubbed away the rubber of the bearning .

Has anyone else had this problem ? My boat was located in Singapore .

Will try to attach a photo .

wow, looks like one of the best abrasives and no wonder it ate the bearing, was the steel good?

The calcium acts as a sandpaper, and starts to sand off tiny pieces of steel.

The tiny particles of steel then join the calcium in the abrasive effect, making the mix “grittier”.

Eventually, larger pieces of the shaft join the mix, creating the damage you are seeing.

The calcium acts as a sandpaper, and starts to sand off tiny pieces of steel.

The tiny particles of steel then join the calcium in the abrasive effect, making the mix “grittier”.

Eventually, larger pieces of the shaft join the mix, creating the damage you are seeing.

Shame on me for not rotating the prop shaft at regular intervils , to keep the part of the shaft in the cutless bearning free of that calcium build-up .

In the attached photo you can see the 3M grey color abrasive wheel on my angle grinder, that I used to grind off the calcium on the shaft .

After the 3M pad cleaning I used the green color buffing compound and a felt wheel to finish polishing the shaft , before replacing it in the new cutless bearning.

I was amazed that there was NO shaft pitting or other corrosion anywhere on the SS shaft , Phew !!!

I’ve heard of similar calcium deposits in stave bearings (aka Cutless bearings) before. And not just in tropical waters.

I understand that the crucial factor is the clearance, measured from the stave bearing to whatever is closest (zinc anode, propeller hub, or line cutter).

The rule of thumb is to have clearance equal to 1 times or 1.5 times the diameter of the prop shaft.

With less clearance, the water in the stave bearing grooves becomes stagnant. And the calcium precipitates out of solution.

Same thing happens inside the raw water hosing and heat exchanger of your engine. And the hoses of a marine head.

I’ve heard of luxury motor vessels, designed not to have enough clearance aft of their stave bearings, that have a water hose that drips freshwater into the shaft tubes.

I suspect that, without adequate clearance, you’d need to hand rotate the shaft about every 3rd day to prevent the calcium deposits.

Vinegar (or another acid) should defeat the calcium.



I hauled out Z on Tuesday. And immediately noted something like 2 mm of vertical play in the shaft at the bearing (maximum play allowed is 1.78 mm or 0.070"). Thought I saw water between the rubber bearing and the naval brass sleeve of the bearing.

My knuckles have almost recovered from the injuries incurred when removing the stave bearing (Zwords.pdf has entries explaining the terms ‘cutless bearing’ and ‘stave bearing’).

I had to drill out one of the blind set screws. And cut the naval brass sleeve of the bearing to get it to move out. Quite inelegant - I clearly would do better with more practice, but I am not volunteering to do it again soon.

Z’s shaft had a light coating of lime in the stave bearing area. Nothing like the coral deposits Douglas reported from Calliste.

This haul-out corresponds with the scheduled replacement of Z’s PYI dripless shaft seal.

I’m thinking of, for the first time, plumbing the dripless shaft seal to the engine raw water coolant flow, so there’ll always be a flow of relatively grit-free water through the stave bearing when motoring. I noted one authority suggesting the standard of 2 gallons per minute of flow through a stave bearing for each 1 inch of shaft diameter! I figure that’s for fast shaft revolution.

When installing the new stave bearing (I chose another brass-sleeved bearing instead of one of the new phenolic resin sleeved bearings), I decided against using blind set screws (those 1/8" hex sockets are easily rounded when I apply force to the Allen key). I drilled and tapped into the brass sleeve, then slipped in two 1/4" x 1/2" pan-head threads and ignored the bottom set screw. Tapping into the brass sleeve might sound excessive, but I’d read seacap’s account of the horror he suffered from set screws that did not do their job.

See attached pic: shaft bearing tube c.jpg.


(edited to identify correctly the metal in the bearing sleeve of the Morse Rubber bearing as naval brass and giving the specs for maximum tolerated play)

looks like an interesting job, what stops the screws from working loose? Friction/loctite? Is there a possibility the screws might warp the inner sleeve?

What is the white material in the photo? Is some of the cutlass bearing sticking out for easier removal next time? The photo is not very clear. I think I’ve replaced ours 3 times in 32 years and about 6000 engine hours. I’ve always had to use a hacksaw blade to get it out–a job I hate. I’ve never had trouble removing the Allen head set screws, put in with a bit of Boatlife sealant. I always wonder if there is a mechanical gizmo, similar to a prop puller that would replace the hacksaw process?
Dan Shaula BCC 59


The white material is the end of the shaft log/shaft tube. I lightly touched a grinder to the area so I could clearly see what was the naval brass sleeve and the rubber of the shaft bearing (aka cutless bearing aka stave bearing) and what was the shaft tube, mishmash or whatever.


I drilled into the brass sleeve of the shaft bearing. And then tapped it. So my 1/4" x 1/2" metal thread penetrates and is threaded into two or three of: (1) the fibreglass of the protuberance of the hull; (2) the fibreglass of the shaft tube; and (3) the naval brass of the sleeve of the shaft bearing.

I’m not concerned that the screws will loosen with vibration. Screws into fibreglass very rarely loosen. Fibreglass has a surprisingly tough grip on metal threads, partly (I suspect) from the friction of GRP and partly from any reaction to the compression exerted by a thread screwing into GRP. That’s why, for example, the sea strainer covering your engine raw water intake is just held by a half dozen screws. And it doesn’t loosen. You may have a few cables and fuel lines in your engine room that are held in place by screws into the GRP. In general practice, they don’t loosen.

If you look closely at my pic, you’ll see that I was a tad over-eager with my saw blade - I accidentally cut into the GRP of the shaft tube (look at the circle of the white shaft tube and you should see my over-cut).

My 1/8" allen key rounded the hex socket of one of the set screws. With nothing else on which to grip, I had to drill it out. Quite inelegant of me.

In frustration, I went to the chandlery and bought those two pan-head metal threads, figuring that next time, even if the philips head fails, I might be able to put grips on the metal head.

I’ve seen various makeshift tools for shaft bearings. None of them elegant. And none 100% successful. Sawing the sleeve is quite common. From my pic you might note that I left the bearing sitting proud, with the idea that I might be able to force grips onto that lip and withdraw it.

I don’t know what boat yards use to extract the new generation of shaft bearings (the ones with phenolic resin sleeves that supposedly swell in water and then grip the inside of the shaft tube). Probably a hacksaw blade!

Seacap’s tale of his slipped shaft bearing is on his own weblog and also at:,9546,page=1


Ahoy Bil , what is , phenolic resin sleeves , I haven’t heard of them before .

I really admire you for your ingenious way to secure a “stave” / “cutless bearing” , in the F / G shaft log , I also like the marrying of SS with bronze , as that has worked for me in many other places .

I do know that BCC Zygote is a ways beyond our sister ships , in maintanince and design ideas .

So , are you still applying Beechems water proof grease , on your prop ?

BCC Calliste has made the voyage on a container ship , back to Port Townsend , at present, Phew !!!

dwkayaks Wrote:

Ahoy Bil , what is , phenolic resin sleeves
, I haven’t heard of them before .

All the chandleries in Aus carry them - instead of naval brass, the sleeve of the shaft bearing is made from a polymer, a formaldehyde resin not very different from bakelite.

The argument in favour of the phenolic resin shaft bearings is that they reduce the mix of metals in the shaft log. And a secondary argument is that, because the resin absorbs water and swells, they are easy when dry to slip into a shaft log. I don’t know how easy they are to extract. And I didn’t compare prices to see if the phenolic resin bearings are cheaper than traditional ones by an amount equal to the cost of naval brass.

So , are you still applying Beechems water proof
grease , on your prop ?

Lately I’m back to my old habit of antifouling the prop, using whatever I used on the hull (in this case, Interlux Micron Extra). Worked okay for the past two years.

BCC Calliste has made the voyage on a container
ship , back to Port Townsend , at present, Phew

Calliste looks in good shape. Well done!



Welcome back! Are you in the yard near Boat Haven? Are you still looking to locate near Tacoma? If you’re in Seattle, let me know and we can get together for coffee or ?.
Dan Shaula

Calliste, you appear to be missing a rudder (unless it is just the ladder blocking the view?)

Hi Dan , Calliste is stored at the Bayshore Storage Yard , about 1 1/2 miles out , before you get to the Boat Haven , when driving to P T .

During the week my wife and I stay at the “Extended Stay America” in Federal Way, just North of Tacoma. Weekends we try to go to the boat .

Gee , Dioscouri , you are correct , the ladder is hiding the rudder .

And yes , it’s great to be back !

nevermind greasing the prop, did you grease the boat to get it in the container?

Hi Stewart , we trucked Calliste on her own steel cradle to the container loading yard , there they lifted all together onto a " Flat Rack " strapped her down , covered her up , then loaded her on a container ship , bound Seattle , from Kobe Jpn .

Many thanks to Bil of BCC Zygote , who taught us how to use the A I S tracking system to follow the ship in port and in transit until it got out of range .

All total a USD 27, K pop , to Port Townsend , WA .

Calliste on Flat Rack sml.jpg

luv the cradle can I start a new thread on that cos I might get my knuckles rapped

Ahoy Stewart , how about a thread , going on about shipping / trucking our boats on trailers ?

Gee , how to get the Forum’s previously posted entries transferred to this category ?

I don’t think anyone wants to re-write their overland , oversea , adventures , shipping their boats .

Attaching a pic of Calliste on a trailer , crossing the Tacoma Narrows Bridge , on route to P T , WA .