Loose C27 Shaft Strut - SailNet Community
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post #1 of 4 Old 11-23-2014 Thread Starter
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Loose C27 Shaft Strut

Boat is out of the water for the winter. Was doing a quick walk around while pulling sails and such. Noticed glistening of moisture where shaft strut meets the hull. Applied some pressure and sure enough there is a little play/wiggle. Sigh...

Anyone had this issue? If so, is there a recommended fix?

Looks like Catalina uses several methods over the years for strut install including both one without bolts and one with bolts:


No idea which one my 1985 has. I do see the hump down below but all glass, no exposed bolts. Judging by drawings the lack of taper in my strut leads me to believe it style 2:
Loose C27 Shaft Strut-imageuploadedbytapatalk1416718933.333201.jpg

Option 1: Start from outside hull, expose edges where strut enters hulls. Align, and squirt in epoxy. Could be done without removing shaft

Option 2: Cut open hump and hope for bolts

Option 3: if cut open and no bolts, secure with more epoxy or replace with new bolt version from CD. Worst case. Expensive strut, shaft removal (rudder drop), etc.

The big concern is that if not fixed the side to side play will cause cutlass bearing wear and/or stress on transmission.

Advice? Thoughts? Experiences?

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post #2 of 4 Old 11-23-2014
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Re: Loose C27 Shaft Strut

Aww Nuts! At least you have the off season to make the repairs...

You are correct in the need for addressing the issue. Vibration, reduction gear output bearing wear, shaft log gland wear, excessive cutlass bearing wear etc. Plus water intrusion into hull layup at the penetration is not good as well.

Given the last point, the best, (and as always the most time consuming) is to pull the shaft (get it check for straightness while it is out) pull the strut, and clean out the original bedding and overlay, allowing for dry-out time depending on what you find..

The biggest problem (other than the grunt work) will be getting the strut in proper alignment (and keeping it there) during the initial bedding. In the yard, a laser alignment tool is usually the answer. A cheap laser pointer shimmed into the the exact center of the cutlass bearing housing and a paper target mounted on the reduction gear flange can be a big help.

Reading thru the linked pdf, it looks as if the big difference is whether the strut mounting is inside the hull (style 1) or in a pocket on the exterior and thru bolted (style 2 and 3) Bolts are added (drilled after alignment) to style 2 and 3 to assist in transferring the load to the hull laminations, as well as holding strut in place while the install resin cures...

Style 1 will be the easiest to remove depending on access inside the hull. In style 2 and 3, separating the strut from the microballoon resin without delaminating the hull looks like it could be a bear... Although, if the strut is wiggling like a loose tooth, the bond has probably already failed.

All in all a dirty job, but not rocket surgery. If you take your time on removal (don't bust nuthin' new 'cept your knuckles) and make sure the initial alignment is right on the money, it is certainly not beyond a diy level.

Your boat will thank you for doing it right, and so will you down the way.

"If the wind will not serve, lay to the oars"

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post #3 of 4 Old 12-01-2014 Thread Starter
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Loose C27 Shaft Strut

Spent an hour talking to Catalina today and they were very helpful. Given the very small amount of play, they recommend injecting epoxy from the outside once dry. Said the install process is similar and injected epoxy is used as the final stabilizer. Should be an easy fix. No need to be overly invasive unless necessary.


Last edited by engineer_sailor; 12-01-2014 at 09:09 PM.
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post #4 of 4 Old 12-02-2014
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Re: Loose C27 Shaft Strut

How will you be able to tell if it is truly dry in and around the strut ?! You could drill holes from the top into the laminate if fig. 1 and inject alcohol to get rid of the water. If fig.2 why not chip out the filler, pull the strut, clean everything, and put back together. As for the alignment issue if you have a new strut cutlass bearing put in you can put the shaft into the strut attach, put polysulfide on the base, put it back up with the bolts holding it loose enough to move around, attach it to the tranny snugly, loose. Before you take it out check your alignment through the stern tube, and note it's position, When you put it back go back to same position. Tighten up your bolts, let the polysulfide kick for about a week, then fill the cavity with a resin milled fiber bog. Now go back in and check your alignment to the tranny, and adjust your motor mounts accordingly if you have to, after the boat has been in the water for about a week to get the hull to settle to it's natural shape!
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