When a 58’ Kady Krogen trawler recently hauled out at Lauderdale Marine Center, our running gear company, High Seas Yacht Service was hired to pull the props and shafts for a routine cutlass bearing and seal service. High Seas Hydraulics was also hired to do routine service on the ABT Trac hydraulic stabilizer systems.
Once we dropped the stabilizer fin in order to replace the lower shaft seals, we found the threaded stud on the bottom of one of the shafts was damaged and had signs of thread damage and galling. This was most likely from a stainless steel nut on stainless steel threads that was installed and removed without the proper never seize. This compromised the re-installation of the stabilizer fin nut so we recommended removing the shaft to repair it in our machine shop, Straight Line Marine. Once in the machine shop, we found that the stabilizer shaft was bent 0.080” which is significant for a stabilizer shaft. When we started the straightening process, which involves applying hydraulic force on the high point of the shaft the stabilizer cracked in two. That was a first – never had that happen before. Under examination of the broken ends it is evident that a crack in the shaft had worked its way to 20% through – we just finished off the job.
This particular vessel is under new ownership so there is limited history as it relates to past problems and repairs. Obviously, this stabilizer was badly damaged at some point in the past. In all likelihood, the boat probably hit something or experienced a hard grounding which lead to a crack in the stabilizer shaft. Over time, these cracks tend to creep and grow.
We were able to source a new stabilizer shaft from the manufacturer and complete the overhaul on the hydraulic stabilizer system.
We have never experienced a stabilizer shaft cracking in two before in our machine shop, but it just goes to show that a small thing such as damaged threads can be a warning sign of bigger issues.