SC-60 Mounting Options

I recently posted a thread with some questions concerning connecting OpenCPN to an AP500, using an SC-60 as the heading source. I noted in that thread that the battery in the processing unit of the SC was issuing a low warning...it had not been changed out in many years. I pulled the unit and brought it to the local Furuno dealer for battery replacement and struck up a conversation about the unit, mounting options and configuring it.

The dealer tech was adamant that he would never install a SC-60 processing unit in the inverted position unless there was no other option available. He said he had seen issues with that mounting approach, but did not indicate what problems had been encountered. For the record, the processing unit in question is mounted to the underside of the pilothouse roof (power switch facing down and the box aligned with the centerline of the boat). The unit was mounted by the original installer (on the other side of North America and long since out of the picture) in it's current location and has been there for many years. I translate the physical mounting position as the "underside of desk - direction A" option in the install manual.

Now, I understand the boat was originally fitted with an SC-50 and the original owner had issues with it. It was replaced with the current SC-60 less than a year after commissioning (about 9 or 10 years ago). The current unit has worked very well ever since. The only issue (other than the recent battery low warning) was the tendency for the SC to lose it's fix in very rough seas or extremely tight port/starboard turns. Luckily, we have a PG500 flux compass for just such situations, but the SC60 is more accurate and does not need calibration every year or so. The satellite compass remains the preferred and primary heading device.

So, I figured I would ask this forum for thoughts on the mounting of this unit in its current location and orientation. Any known operational or performance issues with the inverted option...or advantages with the deck or bulkhead alternatives? Should I be considering relocating the processing unit...or leave it where it is?

Regards,
SteveCo in St. John's

Hi SteveCo,

Mounting in an inverted position is fine, as long as it is set correctly in the menu. If the position was not suitable, the unit would lose heading any time it moved as it compares GPS heading with rate sensor heading. If the difference between the two is too high, the unit will get an "aborting" alarm.

Thanks! After replacing the backup battery in the processor, I did reinstall in the original location and it is again working fine. Will leave it there unless we have further issues...which I do not anticipate.

Regards,
SteveCo in St. John's

I have an SC60 which has worked well for a few years. It now gives intermittent heading failure. The symptons are: GPS1 and GPS2 usually see 10 or more satellites and give good results but GPS3 always seems to report about half the number of good signals.

We swopped the cables at the SC50 end and the loss of satellites moved to another channel so I duess the processor is working. SO it is either cable or the antenna itself. Outwardly there is no sign of damage. Anyone have any experience of the most likely fault? I have a spare GPS13 and GPS17 antenna on board. Is it possible to replace just one antenna on the SC603 antenna using parts from my spares? Getting to the masthead is also not easy, so any other diagnosis tricks would be useful!

FOLLOW UP:
We dismounted the antenna and confirmed it is GPS #3 in the dome which is weak. Very easy to remove and replace - but with what? It looks like the inside of a GPA-19. Can anyone confirm this or offer help as to where to find a replacement. Vessel is in Myanmar so no Furuno agent!