Battery voltage at idle and higher rpms

[BeerMonkey]

after fixing some electrical problems caused by the previous owner and installing a second battery i wanted to check to make sure the charging system is working and i dont think it is. with a volt meter on the - of the starting battery and the postive on the main lead going to motor(also tried on battery post didnt make a difference) at idle i get 12.6 at 3k rpm i get12.8 this is out of the water on muffs not in gear should it be around 13-14 v, what do i check first to see why its not working?

 

[BeerMonkey]

Re: Battery voltage at idle and higher rpms

after doing some searching i see it should be around 13v at 3000rpm, guess ill dig into the service manual and see wht i need to spend money on now.

 

[HighTrim]

Re: Battery voltage at idle and higher rpms

You are not charging fully. What type of motor are we talking about here? Start by cleaning the connections and testing the stator/alternator.

 

[BeerMonkey]

Re: Battery voltage at idle and higher rpms

its a 89 40hp evinrude. in the service book it say how to test the stator but thats it, is there a way to test the rectifier?

 

[HighTrim]

Re: Battery voltage at idle and higher rpms

If it is not a wiring/connection problem, likely that stator.

There is a thread by Joe Reeves in the FAQ for testing the Rectifier. Check it out.

 

[Outsider]

Re: Battery voltage at idle and higher rpms

I suspect the alternator in that year motor is a little anemic even when working perfectly. Typically, full output isn't reached until nearly full RPM, so I'm not sure anything is wrong if you're getting 12.8/12.9 from that size 20 yo ...

 

[Boatist]

Re: Battery voltage at idle and higher rpms

Your battery is not going to charge right unless you get 13.8 volts or more.
I would ask what is the battery voltage before starting?
What is the current output of the charging system suppose to be?
Last what happends if you connect a small charger to the battery and charge. Does it go above the 12.8 volts?
What electrical load is on the battery? Depthfinder? GPS? Radio?

If the battery is normal 12.6 at about 70 degrees with the motor off and only a light load then it should charge when you start the motor. A big battery with a small charger can take a long time to change voltage but need to get at least to 13.8 volts for a full charge.

 

[BeerMonkey]

Re: Battery voltage at idle and higher rpms

ill check those voltages asap. i run 2 batt one is just starting and lights and radio if we are moving and the other is when ancord for lights and radio

 

[BeerMonkey]

Re: Battery voltage at idle and higher rpms

ok its def not charging, im going out now to test the stator and rectifior after i fixt the bronken trailer lights.

 

[jlinder]

Re: Battery voltage at idle and higher rpms

AI don't know, but I have seen a number of posts that indicate that outboards don't put out that much current.

I also notice that you said you added a second battery. How big are both?

Could this be the reason for low charge voltage? With the voltage you are reporting it looks like it is trying to charge but not enough. Maybe the outboard is putting out all it can and trying to charge 2 batteries is just too much?

Perhaps someone who knows outboards, and this outboard in particular can answer?

 

[BeerMonkey]

Re: Battery voltage at idle and higher rpms

i have a perko batt switch and dont put it on both ever, just 1 for starting and 2 for sitting whith radio/lights on.

 

[Silvertip]

Re: Battery voltage at idle and higher rpms

That motor should have a 12A charging system.

 

[BeerMonkey]

Re: Battery voltage at idle and higher rpms

all i can find in my service book are info about a 4 amp system, which seems really small

 

[jlinder]

Re: Battery voltage at idle and higher rpms

What is the second battery for? trolling motor?

If the charging system is 4A or 12A that is not much considering you may be trying to recharge 2 batteries.

 

[BeerMonkey]

Re: Battery voltage at idle and higher rpms

im only trying to charge 1 batt , the starting/running battery. i have a second deep cycle that i run the radio with when we are stopped(swimming/fishing) i use a perko switch and use only the starting battery when moving and only the second battery when stopped, NEVER both at the same time. i know it may seem overkill to run a 2nd battery for just a radio but after having a dead starter battery on the lake im not letting it happen again.