Advanced Stabilizer troubleshooting-

Stabilizer trouble shooting  in Exotic Places

We trekked back to Georgetown from Thompson Bay, Long Island on one stabilizer; which actually delivered a pretty good ride. I’d heard that one would give you about 60% of what both stabilizers do to calm the roll of the boat. And now, I agree.

We had 4-6 foot seas off the starboard bow, close to a beam roll. We tucked in at the southern entrance to GT to stay behind the islands that protect Georgetown harbour. We were amazed at the sheer number of boats.

Soon enough we were exiting Conch cut and back into the nasty ocean swell, but only for about 10 miles, before we made our way into Emerald Bay Marina. I was concerned about getting into the cut with the seas, as the entrance is almost due east. But it was okay, and we were soon docked safely at the marina.

I flew off to Ft Lauderdale to pick up and hand carry the Rexroth servo valve, which should fix the port stabilizer issue.

I got the part, wrapped it carefully in my clothes, bought some fishing tackle and a Skyroam device for internet connection after we left the Bahamas.

I had a fun couple of days with Michael and Katie and Penny. And was surprised that Rob and Becky from Manatee was there for one day. So the party did indeed go on.

Michael and Katie are well, they purchased their dream property in the Gold Coast, near Byron Bay. It is a huge empty parcel of grazing land. They are working with an architect to design the house, fully self contained, off the grid.

I learned that they are planning to ship KYA, their Nordhavn 68 back to Australia, rather than sell it in the US. I was thrilled to learn this.

And so the repair of the stabilizer was soon to happen. With servo valve in hand I came back to Georgetown, at Emerald Bay. The weather promised to get crappy again, so we decided to leave the marina, due to the horrible surge from waves that are from the northeast and headed back to Georgetown craziness.

We found our spot in Sand Dollar Bay, and there were 4 other Nordhavns, and New Zealand friend Devon on Pura Vita, a Beneteu 435.

News was just starting to heat up about a new virus, known as the Corona Virus, due to the shape of the virus at the molecular level.

I installed the new servo pump on the port stabilizer, and we were both devasted to learn, that the problem was not fixed.  And so the incredibly frustrating hunt to locate the problem continued.

Devon came over one afternoon, to help problem solve, as did Gale Plummer off of Work Not, N57.

I contacted Daryl at ABT Florida, and Dave at ABT HQ in California. I later got a call from James Knight of Yacht Tech, to connect me to his man, Tony Field who also is an ABT expert.

We tried to narrow down the issue. I had to start a log of the steps I had taken to keep them straight and to tell my panel of experts. It is copied below.

So this issue first occurred in the Raggeds 24 Feb and we figured it out finally on 11 Feb we diagnosed and repaired the issue. Fortunately, the servo valve can be returned for credit.

I am so thankful for both Devon and Gales’ help and support. Gale and I finally determined that there was a block in the check valve after he came over and started bleeding the cylinder.

Also great thanks go out to the team at ABT, and to Tony Fields at Yacht Tech. I really do appreciate your help.

I know I sure did learn an awful lot about stabilizers and their troubleshooting.

For those that are interested follows is the painful troubleshooting process we went through.

ABT failed port stabilizer diagnosis-                                       Southern Star 6-3-20 Concluded 11-3-20

Failure of Port side ABT trac 220 occurred about a week ago. In fairly benign conditions started the stabilizers and the port stabilizer drifted off center and would not respond to any commands to center or to activate.  Starboard side worked normally. Put stabilizer in free mode to manually center- shows center on display.

Port stabilizer cylinder was replaced about 250 hours ago.


  1. Switched control cables at control box- #1 and #2 to confirm the logic on the control board was good. Switching cables changed the display to show the drifted stabilizer on starboard display (actually port). Port on display (actually stb) is normal.
  2. Switched control cables to correct position, port side back to drifting.
  3. Check manifold hydraulic pressure 1350 psi
  4. Cleaned all connectors.
  5. Check continuity on all pins at control box to port stabilizer connection at port stabilizer- all pins show continuity.
  6. Warm to touch solenoid dump valves x2 on port side stabilizer, Servo valve also warm
  7. Put port stab in free position and pin fin in center position, display shows pin centered.
  8. Purchased new servo valve from ABT, installed and test. SAME FAULT.
  9. Remove “Y” cable from Starboard stab- exchanged both cables.  Port fault continues, starboard works normally. Proved y cable not at fault.
  10. Put fin in free position, move fin physically from the water through full range of motion, display accurately shows fin movement.  Proved sensor is not at fault
  11. Use new potentiometer, fin sensor, inserted into y cable. Slowly move sensor through range, display shows the correct movement.  Sensor not at fault
  12. Open control box- check all fuses- all good
    1. Reverse cables again. Bad fin migrates to starboard display.
    1. Reverse dump valve cables at same time- same as above
    1. Check voltage on servo valve command on port side- showed -9 v
    1. Check corresponding wire at servo valve connector- showed same 9v
    1. Proved control box not at fault, and control cable seems okay.
  13. Check pressure on port and starboard  at servo valve- port is 1350 psi
  14. Starboard stab Check pressure on top of servo valve manifold- starboard 600/800
  15. Port stab- no pressure on either test ports on top.
  16. Removed both servo valves- put old port on starboard- starboard on port- RESULT- port side still not functioning- Starboard is normal – Servo valves are not at fault.
  17. Found enough cable on each actuator to reach to opposite side- switched port control cable and starboard cable- fault remains on port stab. Proved Control Cable not at Fault
  18. Tony Fields – Centered both stabilisers. Leave power on, no engine run, check each dump solenoid in 20 minutes. Port valves warm to the touch, 100 &106 f. Starboard side hot to touch.
    1. Check voltage at solenoid and resistance.
  19. Checked dump coils
    1. Port. 21.8 volts, MB 35.3 ohms, MA 35.4 ohms
    1. Starboard one conductor very corroded. Removed and cleaned. 22.6 volts, MB 36.4 ohms, MA 35.3 ohms
  20. Changed out port cylinder with rebuilt spare. Did not connect it to the fin. Left it free. Used spare position sensor to find center on the display, started engine for hydraulic power, moved sensor back and forth to simulate fin movement in active mode.  Also observed cylinder when center command. No Response from cylinder. Conclude that the cylinder in the system has not failed.
  21. Removed dump valve solenoids on port to test their movement. They are normally open and close when energized.  Removing the valves meant the oil leaked even with the valve under the reservoir closed. Alarm went off which shut off any function to the coils, and dump valves.
    1. Removed valves and tested them with another 24v power supply stern thruster. Both dump valves moved.
    1. Crossed the dump valves with the starboard side- exchanged MA and MB valve and coils. Refilled oil tank. Tested, run engine. Starboard side normal- Port side still not responding.  Proving dump valves are okay.
  22. Gale from Worknot came over to diagnose the hydraulics
    1. Started stabilizers and engine.  Let stab go to free, tried to center. Then crack hyd hose on cyclinder-going to A side- and the shaft moved back toward center.
    1. Tried this a few times, and determined that the B side was working
    1. Removed valve 120 – four way valve- first on B side- looked clean and normal.
    1. Removed valve 120 – on A side, and discovered an oring in one of the chambers, with parts blocking the orifice. Cleaned out with a small needle.  Removed oring bits. Reassembled both valves into same corresponding places.
  23. Start and test system and both stabilizers are working normally. Next day check all hose and other connectors and test run. Seems to be normal.
  24. Changed hydraulic reservoir filter, topped off tank.


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