Outboard alternator

[Ratherbfishing]

I have a 25-horse Evinrude motor.  It is an excellent motor and, when primed properly at the beginning of the day, starts usually after just a few revolutions.  And later starts require just a quick tap on the starter button (I may start the motor just 10 or 15 times a day). I've noticed, however, that at the end of the day, the battery (freshly charged in the morning and only a year old) requires some charging.  My question:  Assuming you don't do a lot of stops and starts, should an alternator keep a battery fully charged OR will the requirements of starting/running a motor tax the battery more than the alternator can "keep up"?  Or should I have the alternator checked out?

[Jig Man]

If you are going short distances your alternator may not have enough time to recharge the battery. What kind of battery do you have?  Series size:   CCA  MCA  RC 

[Ratherbfishing]

19 minutes ago, Jig Man said:

If you are going short distances your alternator may not have enough time to recharge the battery. What kind of battery do you have?  Series size:   CCA  MCA  RC 

It's a standard lead acid cranking battery.  Size?  Without looking at it, unsure.  Not huge and not small.  Many of my runs during the day are not long.  Perhaps 200 or 300 yards.  Just enough distance to not want to use the trolling motor.  The run at the end of the day is usually the longest.  Perhaps ten minutes (or longer if we're slow trolling in).  Distance is the same, though (obviously).

[Jig Man]

My outboard always requires some charging when I get home no matter how far I run.

[Way2slow]

Unless you are making long runs, it's almost a sure bet your cranking battery is going to be partially discharged by the end of the day.

There have been studies done on professional's cranking batteries at the end of the day during tournaments and on average, their batteries were only approximately 80% charged.

That's why most people than know, use onboard chargers with enough banks for every battery on the boat, including the cranking battery.

I don't know the year of your motor but in all probability, it only has about a 16 amp charging system, so it's not exactly a power house when it comes to charging the battery.  If you want to make sure it is charging, take a voltage reading across the battery terminals with the motor turning at least 2,000 rpm.  You should have at least about 13.8VDC

[OnthePotomac]

My boat has a 60 Yammie (now 18 years old) and the manual on the motor states that the alternator will not begin to charge until the motor is running at 1600 rpms.  I run several miles at a time on the river, so the battery stays well charged.