797 shut down problems

When I go out I have my 797 running by the time I get the boat in the water. I often run 15-20 minutes to where I will fish. I then troll for hours sometimes. The last couple of times out, the 797 has worked fine going out and trolling, then when I crank the big motor to move or head in it will shut off. I hit the power button and it comes back on for from a few seconds to maybe 30 seconds and shuts off. It will not stay on while running the outboard. If I move, it again works fine while running the trolling motor but shuts off when I crank the outboard. It also seems to be warm on the top back of the display unit. It is connected to the cranking battery and I always get a low voltage pop-up when I crank.

Anyone else have this problem or suggestions?

I would say a weak battery or a loose wire or both make sure its clean. You can bring a set of jumper cables and jump off your trolling battery when you start and see what happens.

My 787 was acting sort of like that, except for mine gave no trouble
AFTER I got the motor cranked... But it would give low batt flag and
go off sometimes later in the day when I cranked up. Found out my batt really was getting
low - first boat I've had in a long time with aerators, etc. and I'm usually
running two df, two gps, two of 'em color - put on board charger on
cranking batt, and so far, so good.

I had similar problem. I installed a separate battery for the electronics. However, I have enough electronics on my boat to bring down the New York Power Grid.;)

If your using a tube type fuse holder you may want to switch to the new spade types. There's been some problems with the tube types not keeping contact.
WarrenMN

Three things other than a bad unit can cause this. Low voltage, high voltage, and a bad battery which causes the first two. A lot of motors, especially older ones do not have regulators in the charging circuit and the battery does the regulating. The most common problem of high/ low voltage is the battery connections. Make sure they are shiny clean and tight. Look for signs of corrosion at the base of the lugs and if you find any, replace them. They can corrode inside where you can't see it. If you can do a voltage drop test, that is even better. After checking all your cables, check your charging circuit. The simplest way to do this is with a volt meter. With the motor off, check the voltage at the battery. Now start the motor and as RPMs approach 2000 RPM you should see a voltage increase. If it increases to around 14-15 VDC, it is working fine.

Thanks, guys. I hadn't thought about a weak battery but since it has no trouble cranking the motor I don't think that's it. I do wonder if the alternator is putting out too high a voltage but if that's it the 797 should shut down everytime I crank up, not just after I have had it on for several hours while trolling or nightstalking.:confused:

Next time out, I'll try hooking it to the trolling batt and see if I still have a problem.

I took Canepole's advice and added another battery to the boat. #4. To save on weight I am useing a 12 volt lawnmower battery under the steering console. I charge it every couple of trips, no issues after 6 weeks of use.