Garmin 740s Cuts Out

[JeffM]

I have two issues with my Garmin GPSMAP 740s, and hope that the experts here can help. The unit was new last year, and these issues showed up once or twice year, but have been more frequent lately.

Occasionally, usually after a fairly good jolt, the unit will shut down and restart. I've checked and rechecked the wiring, connections, and fuse, and all appear to be good and tight. The unit is mounted on a RAM mount attached to the windshield support pole, so there's a little shock-absorption through the mount, but not a lot. Has anyone else experienced this?

The other issue appears to be related to the transducer. It's mounted on the transom, midway between the trim tab and the outdrive, aligned as shown on the installation instructions. However, when I'm on plane, the depth display will frequently begin to blink, and does not change. When I come off plane, it begins working properly again, and once in a while it will simply start working again when I'm still on plane. As best I can tell, the blinking starts after crossing a large wave, or the boat pitches at a somewhat steep angle. Again, has anyone seen this, and what (if anything) can be done to fix it?

Thanks in advance!
Jeff

 

[Lazy Daze]

If you're positive that all +/- connections are solid, then I would think something is going on internally. I would call Garmin. Did you buy it from Garmin or a Garmin dealer? That would be helpful if you did.

Is the transducer lined up with a lifting strake? Are you sure it's below the hull enough? Is it angled correctly?

 

[src]

I have a 540 that is doing the same thing. Out of warranty, of course. I'd be interested in hearing what happens with yours.

It also had an issue with the depth losing lock, and simply adjusting the angle of the transducer worked for me. You may have to play with it a bit to find the right position.

 

[Bob a Buoy]

My last two garmins did the same thing. All connections were solid and we could never figure out why it happened. I will never own another one. I like the units and from what I hear, customer service is great, but having my gps cut out on me randomly is unacceptable. My last two Lowrance units have performed flawlessly.

 

[JeffM]

Thanks for the responses!

Lazy Daze: no, it's between the outdrive and the first strake; I believe that keeps it under water all the time, and it should be far enough from the drive to minimize interference. I have made sure the electrical connections are tight, and secured the wires and harness so it isn't exerting pressure on the connections.

Bob a Buoy: I followed the installation instructions carefully regarding, angle, but I'll recheck.

I do like the unit. It's easy to read and the programming is straightforward and intuitive. I've set it up so it reads depth below the hull and configured the display to include the info I want. As src said, though, having it cut out randomly isn't going to cut it.

 

[deenbob1]

I had a similar problem with my gps and was told to press on the unit's face plate in several places. The face plate plugs into the main board and pressing on the connection point (where ever it is?) might clear up the problem. When I did this the problem did go away but only temporary.

 

[JeffM]

Thanks for the suggestion. On mine, the unit restarts almost immediately.

 

[Bob & Sue]

I had a similar problem with both Garmin then tried a Lowrance happened with both if I hit a wake or sometimes moved the cabin door the only thing that would go out were the Chartplotter, Fishfinder & factory installed depth gauge. I rewired the gps checked every wire then it came to me the gps & factory gauge were on 2 toggle switches Depth & ACC so it was something they had in common. 5 minutes of looking at the wiring harness I found one of the 3or4 plugs that feed the dash had come loose on one side causing it to loose contact, plugged it in no more problems.

Put all the Garmin electronics back in 2 years ago haven't had any issues. Sounds like you might have a similar gremlin, maybe you could borrow another unit and see if the problem goes away, also check your electrical manual to see which # plug is bringing power to the unit might even be one of the connector pins have come loose or a bad solder.

As far as loosing depth I have used both Garmin & Lowrance transducers both would loose depth on plane depending on your transducer which is probably an Airmar I found that having them just over 1/8" below the strake gave me the best results. Check garmins site for your transducer it may only be accurate up to a certain speed or you may need to lower it another 1/8" to keep it out of turbulent water. You can test this by getting up to speed where you drop the signal come back down in speed till you have a good depth signal, now turn boat hard to port & starboard several times if you loose signal transducer needs to be lowered, it's in turbulent water.

 

[MonacoMike]

Jeff, I agree with Bob the problem is likely a gremlin in your wiring harness rather than something in the actual device. I have a 440S and a 740S and if the voltage drops too low when cranking the engine they always shut down. So if you're getting a break in the circuitry it's going to shut off and then it will it fire right back up. I also had a pin break in one of the wiring harness plugs last year and it took quite a long time to figure out where the break was. You literally need to tug on every wire to make sure it doesn't come out of the plug.

I'm betting this is the issue, not the device.

MM

 

[src]

Just remember that the instruction manual doesn't know anything about your particular boat. I figured that bow rise while on plane was throwing my transducer off, so I angled it further back to attempt to keep it level while cruising. Never worked. On a whim, I angled it a bit forward and it worked like a charm.

 

[JeffM]

Thanks for the suggestions -- next weekend is a work weekend on the boat, so I'll add checking the wiring harness (again), and fiddling with the transducer angle and depth below the bottom.

 

[JimFromMD]

Not that it will help with your mounting issue, but as another data point for the 740, I have an in-hull transducer (vs through hull). The mount is siliconed to the hull inside the bilge and then filled with fluid (I used winterization pink antifreeze). As long as the fluid is full in the mount, the depth reading is rock solid. When watching the bottom contour mode on plane it can flake out with some chop, but the actual depth reading number is almost always solid.