Motor won’t do anything all of a sudden

[tnbassin]

My 2017 Mercury 115 4 stroke sometimes won’t start in the middle of the day. No power. All of electronics stop. It has now happened 3 times out of about 7-8 fishing trips. It isn’t the starting battery because last time it happened it was 70% charged when it happened. Stupidly didn’t check that on the first 2 times. Just assumed the battery was dead and charged it. This last time I also had the starting battery checked out at Advanced Auto and they said the battery was good. Even though it was 70% charged, it sure acted like a dead battery. I did have all my electronics and livewell on throughout the day. I was able to start the motor using one the trolling motor batteries. Weird part is that the first time it happened, I was able to get it to started by flipping the kill switch on and off. I just assumed that I had pulled it down slightly. Then it happened again and on this second time it happened, the kill switch flipping didn’t work. I had to boost it off with the trolling motor battery. Third time, no luck with kill switch again and had to boost it again with the trolling motor battery. Any ideas? Could the kill switch be going bad and causing this? If not, any ideas on what else it could be?

[ch]

Sure sounds like a weak starting battery. U got any buddies that would maybe let u borrow the battery out of their boat to see if u get the same results?

[ECobb91]

Sounds like something is drawing too much power when you are trying to start because if it was a bad kill switch the graphs would remain on when you turn the key but since they are shutting down, something is pulling too much current. Try turning off the front graphs and the livewell but keep the console graph on with the info screen that shows how much voltage is left on the battery. When you turn the key, only turn it enough to turn the master power on and power the gauges, the. Look at the graph to see how much the voltage drops. if it’s significant, there could be a loose connection some where along the gauges that is drawing too much power from the ignition. The only other test you could do is shut everything down before you start the motor and see if it does it again. If it does then it’s just a bad battery or bad ignition switch.

[ranger521znem]

Try to see if the battery cables are tight enough. This happened to me one time. First grab the actual red wire and try to wiggle it. If it moves its not tight enough. then try the black wire to the battery. If its loose use an adjustable wrench or another tool to tighten the wing nuts or regular nuts real tight. Also a small amount of crud on the terminals will cause this. Its simple but hope its it bc its simple fix hope this helps out then you can check the battery get a multi meter to see if your batt is dead or not its a good tool to use. you can google how to use it for checking your battery on you tube.

[billnorman1]

70% ain't too good but: since you manipulated the kill switch there may be an issue there. If you're referring to the motor kill switch you should be able to isolate that. If you're talking about a battery isolator switch which removes the battery from powering the boat, then that could indeed be the trouble.
Since it starts when jumped from a trolling battery it sure sounds like the battery is bad unless you have a connection issue at the battery or the battery is no good.
What is 70% charged?
When you say it doesn't start do you mean it won't turn over either or it turns over but won't run?

[Bass Pro Shopper]

Sounds like the battery is dying. I had a similar issue with one that was 6 years old. Replaced it and no more such trouble. How old is your battery?

[tnbassin]

The 70% charge was from one of those cheap hand held battery meters (not a voltage gauge) that shows you how much your battery is charged. Put the clip on the negative side and then touch the positive post.

The motor will not turn over or do anything. Turn the key, nothing.

Battery and motor is 1 1/2 years old. Battery is a Interstate 27

[mrdeath]

Bad connection somewhere. Even with a weak battery, it should do something. Does the tilt/trim work?

[ToBo]

Try to see if the battery cables are tight enough. This happened to me one time. First grab the actual red wire and try to wiggle it. If it moves its not tight enough. then try the black wire to the battery. If its loose use an adjustable wrench or another tool to tighten the wing nuts or regular nuts real tight. Also a small amount of crud on the terminals will cause this. Its simple but hope its it bc its simple fix hope this helps out then you can check the battery get a multi meter to see if your batt is dead or not its a good tool to use. you can google how to use it for checking your battery on you tube.

Agree with this. Clean and tighten all battery connections and verify voltage with a digital multimeter.

[Cheeseman]

70% ain't too good but: since you manipulated the kill switch there may be an issue there. If you're referring to the motor kill switch you should be able to isolate that. If you're talking about a battery isolator switch which removes the battery from powering the boat, then that could indeed be the trouble.
Since it starts when jumped from a trolling battery it sure sounds like the battery is bad unless you have a connection issue at the battery or the battery is no good.
What is 70% charged?
When you say it doesn't start do you mean it won't turn over either or it turns over but won't run?

^^^ This

Since it starts immediately when you jump it off of the TM then the starting battery either has a poor connection, or it is on its way out.

[marinetechnician]

With a multi-meter that should be very simple to diagnose. If you are not good at this find someone who is. A good auto tech would know how and what to check if you know any.

[Tequila Sunrise]

Do you have battery terminals that you have added or are your starter wires run to the threaded bolt? It sounds like a bad connection.

[bassnman81]

I think if you have a bad battery switch then jumping with the trolling battery wouldn't work either. I bet it's time for a new battery.