The incident

An offshore support vessel (OSV) was underway to field loaded with cargo when a sudden drop of starboard main engine RPM was noted.


The main engine dialog screen gave the error message <invalid throttle signals>. The engineers informed the bridge immediately. Investigation began, while the onshore office and the client were also informed.

It was decided to take the vessel back into port as a quick fix was not available.

Probable cause

As IMCA informed, three reason led to this problem:

  • The remote speed controller module had failed;
  • The cause was overheating for a prolonged period;
  • The root cause was assumed to be extremely unfavourable conditions (hot and humid) in the engine room, leading to unexpected and unpredictable failures of electronic components because of high temperatures.


In such cases:

  • Crew should remain aware of and alert to the likelihood of unexpected equipment failure under extreme conditions of heat;
  • Sufficient spares of potentially vulnerable electronic items should be carried and stored appropriately.