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Transom gudgeon bolt length?


New Member
Noticed the other day that my transom gudgeons and associated bolts are showing signs of corrosion and need to be replaced. One bolt head is already cracked off.
Boat is currently in dry storage near Phoenix about 2.5 hours north of my home in Tucson, Arizona.
I've bought new gudgeons but would like to know the length of the bolts I need before I head up for the repair.
I know they are 1/4-20 thread with a 7/16" bolt head but do not know the length without first pulling one out.
I know I should have thought about that before I left the boat.
But does anybody happen to know the approximate length of the transom bolts. I'm guessing maybe 2".


New Member
Figured it out this past weekend. Bolts are 1/4-20 thread by 2" long.
But project was a bust on two accounts. Did not realize that there are two lower transom gudgeons stacked on top of each other for the bottom assembly. The top is a single unit. Also the replacement Schaffer gudgeon that I bought at APS has a slightly different hole spacing than the factory gudgeons so you would have to wallow out the holes through the boat if you go this route. There is about 3/16" in difference between the two. I'm now going to clean and carefully inspect my old ones and try to reuse them. I'm also going to install an aluminum backing plate as the interior surface is quite rough and irregular and the SS backing plate I made might be too stiff to evenly spread the load on all of the bolts. Good news is that hull and plywood transom is still in good condition despite the corrosion and 4 sheared off bolts. Photos attached of existing condition. I'll post new photos once the project is complete.Transon Gudgeon Exterior.JPGTranson Gudgeon Interior.JPG


New Member
Successfully finished the gudgeon bolt replacement project last weekend. I used 1/8" thick aluminum backing plates. I found that that a stainless steel plate was too stiff and would not conform to the irregular interior surface. Also used 2.5" long bolts for the lower gudgeon which are probably a little too long and I have some fear that the nuts may have been close to bottoming out on the short bolt threads. Used 2.0" long bolts for the upper gudgeon which seamed to be just barley long enough but okay. At some point I may change out the lower bolts to 2.0" lengths. Also used 3M 4200 fast cure sealant to make everything watertight. Completed photos below:Lower Transom Gudgeon Interior Plate 2.5 in Bolts.JPG



New Member
Nice job BFD. Good call on the Alum vs stainless as I went to put the stainless back on and holes were too tight so it got a little 4200 messy.

I just did the same job and fwiw, I found the Racelite gudgeons cheaper and the bolt holes lined up perfectly. The Racelite folks are great and product is made in Ohio.


Steel bolts on an aluminum plate will create a galvanic reaction. The two metals will create an electrical charge and eventually the steel bolts will infuse themselves into the aluminum. I have used aluminum plate as backing plates for my winches and all the stantions. I made the hole in the aluminum plate bigger and used a Teflon washer/collar to separate the bolt from the plate. The plate will hold but in a few years it will be very difficult to remove or adjust the bolts.

Good luck, fair winds.