Be careful with the Garmin units. Apparently the newer chartplotters use a nice strong magnet to keep the door shut on the cart slot. I only realized this after purchasing a Garmin 740s chartplotter radar package - when I got it home and read the installation instructions, I noticed that it was recommended that the plotter be mounted no closer than about a meter from any compass, which makes it pretty useless if one intends to mount it at the helm. (This was positive reinforcement for the principle of "RTFM" - Read The Friendly [[I]or whatever adjective you prefer[/I]] Manual first).

Further inquiry on Sailnet ([url]www.sailnet.com/forums/electronics/72909-chart-plotter-interferes-compas... ) revealed several threads discussing this design foible. See [url]www.sailnet.com/forums/electronics/68153-garmin-740-radar-question.html[... ; [url]www.sailnet.com/forums/electrical-systems/65905-gps-compass.html[/url] ; [url]www.sailnet.com/forums/gear-maintenance/63401-binnacle-compass-obsolete....

Before proceeding further, I took the chartplotter unit over to the boat and, sure enough, it swung the compass about 20 degrees when held nearby (although when held above the compass it only seemed to swing it a few degrees). Not a good idea.

I returned the entire package to the local WM store, and the staff there indicated they were surprised and agreed that it was a ridiculous design as well and that they would no longer recommend Garmin units with the magnetic latches (they were all sailboat owners, so they immediately understood the absurdity of something like this being anywhere near a binnacle compass). On a more recent visit, they told me that they have now complained to Garmin about it, and Garmin said that if owners open the case and remove the magnet it wouldn't void the warranty -- but who wants to take that kind of risk?
Too bad, seemed like a nice unit for the money.

Is the RL70 still working? Intersting in selling it?
Let me know. Mine died and I don't want to buy a new one.

As a result of Mathew's post regarding the mounting of the Garmin unit with respect to its proximity to a magnetic compass, I was looking at the Raymarine C90W installation instructions. In there it also states the display should be mounted at least 3 feet from a magnetic compass. I wonder how many C90W's are mounted at the binnicle??

I suspect that most manufactures have this type of recommendation in their installation instructions. If the magnetic interference from these units is consistent, then an adjustment of the compass correction bars should eliminate any magnetic error.

[QUOTE=tgrover;8353]As a result of Mathew's post regarding the mounting of the Garmin unit with respect to its proximity to a magnetic compass, I was looking at the Raymarine C90W installation instructions. In there it also states the display should be mounted at least 3 feet from a magnetic compass. I wonder how many C90W's are mounted at the binnicle??

I suspect that most manufactures have this type of recommendation in their installation instructions. If the magnetic interference from these units is consistent, then an adjustment of the compass correction bars should eliminate any magnetic error.[/QUOTE]

That's disturbing news -- I was thinking about the C90W as an alternative. However, although I'm certainly not qualified to opine of the subject of compass correction adjustments, I would not be comfortable relying on a compass that had to be compensated for a 20 degree swing caused by a close-by magnet, particularly because there's no reason to expect that the swing would be consistent on all courses.

I presume any electronic device is capable of some compass interference. But clearly a device with a magnet deliberately built inside is not a good thing to have at a binnacle.
In a post by Maine Sail on one of the threads I linked up to above in my prior post, he noted that the older Garmins did not have this problem, recommending the older 3200 series (new ones can still be found with some assiduous Googling). And other commentators as well noted that other older Garmins did not have this issue, so it would seem obvious that the manufacturer(s) could avoid it with a small redesign....

I replaced with Garmin 10" chartplotter and HD radar. It aslo required a new pod. Love the unit and its features.

I have a new Garmin 546 with the magnet. If I hold it level with the compass, the compass will swing about 20 degrees. When I hold it above the compass about three inches it does not effect the compass. The instructions say to mount the 546 twenty inches from the compass.

I contacted Garmin an inquired about removing the magnet. Their reply was "...any type of modification done to the device would void the warranty." I sent another message back to Garmin asking if they had any solution to the magnet/compass problem or should I return the 546 and buy another from a different company. They have not sent a reply to this last message.

I have owned a Garmin GPS of one type or another for over fifteen years and do not want to have to learn to operate a differnt brand so I am fabricating a braket to hold the unit about three inchs above the compass in front of the pedestal where it does not effect the compass at all. I have a short pedestal not the newer high arch type so the 546 clears it with no problem.