motor doesnt seem to be charging battery

[toddy]

Purchased a new boat last spring - 16 ft lund with a 40 hp mercury tiller. Motor has EFI.

Thing worked fine last year. And appears to be working fine this year but I noticed something odd back in May when I was crappie fishing.

The fish finder (garmin downview i think is the model) was showing my battery voltage around 11.8 while the boat is running. Normally it would be up around 13.8. The motor was starting fine so I actually thought there was an issue with the fish finder and maybe the way it was connected after it came out of storage.

The boat sat for a month before I used it again but I took a voltmeter to the batter and checked it before I put it in the water. It read 12.4 volts. I thought it should have been higher but it had been sitting for over a month since last use. I went fishing on Saturday and the fish finder was reading 11.8 again, but would read 12.0 v when the motor wasn't running. When the motor was running I put the voltmeter on the battery and its reading 12.1 volts. Clearly not the fish finder as its close to the real voltage. After trolling for an hour strait I checked the battery again while the boat was running and it still read 12.1.

I know for a fact that if the battery voltage drops below a certain voltage while the motor is running it will quit as the motor draws from the battery while it runs and it charges at the same time.

At first I was thinking this may be an issue with the charging system on the boat but I am second guessing that its possibly the battery. Battery and motor are both new in 2017. Any thoughts?

motor is under warranty but I hate the idea of losing the boat for a few weeks if I have to take it in.

[GYPSEE]

A good dealer will have you in and out in a day.. worst case Ontario, you drop it off Monday, and pick it up Friday

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[Deer Wrastler]

hmm maybe something shorting out? I normally show 12.5ish on the FF and maybe 12.2 when running. Seems like something is soaking up the current.

[toddy]

It turned out to be a fuse.