Cracks at rudder mount

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Dec 10, 2012
Hunter 18 Raleigh
Hi all, while under sail in a strong breeze I recently noticed some "give" in the rudder mount and some cracks in the sealer around the top of the mount. Closer inspection revealed some cracks around one of the mount holes. I removed the bracket (the screws did not seem very tight) and scraped away some of the sealer that coated the underside:

Here is a closeup of the cracks around the upper left hole:

After removing the rest of the sealer, I see what appear to be plugs into the hull in which the screw holes have been made... is this a prior repair or is this how it was originally made? (We purchased this boat used 2 years ago). All six screw holes appear to have been repaired. I am not sure what the repair material is - epoxy or fiberglass maybe.

So how best to repair this? Try to inject epoxy into the crack? Has anyone had to repair a rudder mount like this? What is under the plastic skin in the rudder mount area?

Also, once the cracks are repaired, what is the best sealant to use under and around the edge of the bracket? I have some 3M 5200 marine adhesive sealant, will that work?

Thanks for any advice/thoughts...


Sep 4, 2007
Hunter 170 Grapevine Lake, TX
Mark, the skin crack can be repaired using the methods that have been well documented in the 170 threads. The only thing to worry about is whether or not you have moisture in the backing block that the rudder attachment is bolted into. Do NOT count on 5200 (the devil's adhesive!) to take care of the problem.

I would start by drilling a hole into the backer block to determine if it is soldly attached to the hull and dry. If it is not, we can discuss Plan B but let's assume the backing block is intact and you need only to address loose rudder bracket screws. It's possible prior repairs including drilling/plugging/redrilling for the screws. I considered this for my boat but rejected the plan for the approach below.

I ended up replacing the wood screws with stainless machine screws by utilizing stainless inserts. After drilling holes for the insert, I saturated the opening with epoxy and threaded three inserts onto a screw used to drive in the insert. I waxed the threads of the drive screw and left it in place until the epoxy set.

The mod held up well after 225 miles of sailing over choppy bays so I suppose I can claim success. I also used this process for the motor mount.

So, I would consider confirming the integrity of the backer block, repair the plastic and install inserts. This allows the use of machine tap screws (screws with fully threaded shafts), a large improvement over wood screws.

Let me know if you have any questions.
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Nov 5, 2012
Catalina 36 Mumbai
I would recommend grinding the area that has a crack and fibre glass it. This is the best method and will last long.
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