Mariner outboard overcharging ??

Mariner outboard overcharging ??

Postby De Wa » Tue Mar 13, 2018 8:46 am

I receintly purchases a new Garmin fish finder. While exploring the different settings I noticed that while running the motor the battery voltage went up to

16.5 volts. In my limited knowledge of this subject, this seems too high. I am concerned that this will damage my deep cycle battery and my fishfinder

What should the motor be outputting to the battery when running/charging ?

If this voltage is to high, what is causing the voltage too be so high, possibly a faulty voltage regulator or rectifier.

What can I do to fix the problem?

Mariner 50 hp 1996 model.
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Re: Mariner outboard overcharging ??

Postby Miles » Tue Mar 13, 2018 9:41 am

Hi

I'm not very clued up when it comes to the electrical side of things, however, i did notice that exact same problem on one of my boats. It ended up being the battery that was busy dying.

Cheapest and easiest thing to check is your battery. Take it to a battery centre and they'll do a load test and will tell you the state of your battery. This is usually a free test.
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Re: Mariner outboard overcharging ??

Postby Pugwash » Tue Mar 13, 2018 10:40 am

Maximum charging voltage should be 14.4v... Normal is 13.8v.

Connect a battery that you know is good and then measure with a meter directly on the terminals with the motor running above about 1000 rpm. I don't suggest rely on the sonar's readout. There's too much wire in between and one can't be entirely sure of it's accuracy.

If the alternator is putting out too many volts, see if you can adjust it on the regulator, but I doubt it... I'd expect it's a solid state one regulator with no adjustment screw. Otherwise replace.
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Re: Mariner outboard overcharging ??

Postby De Wa » Tue Mar 13, 2018 11:29 am

Thanks for the advice.

Will check the battery.

I don`t think it`s the battery as I had lights on most of Saturday night while fishing and the motor cranked with ease when starting the next morning.

Will borrow a battery and check running motor over 1000 rpm
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Re: Mariner outboard overcharging ??

Postby willem wikkel spies » Tue Mar 13, 2018 9:10 pm

not so fast..............

we are talking about 2 stroke motor here.
thus no alternator!!!!

two strokes have a "coil" for charging and a coil for lighting.

thus the faster the motor spins, the higher the voltage made.

the voltage made is ac or alternating current.

then there is a rectifier, which makes ac volts dc volts.

there is also a balance between the electricity made and the current produced.

thus, the slower the motor turns, the lower the voltage, the higher teh current produced.
the higher the revolutions, the higher the voltage, the lower the current produced.

so it is all in balance.

normally a regulator is fitted on a certain size motor and upwards, where teh smaller motors only have rectifiers, so no voltage regulator.

ok, the next step is the battery.
they call them leisure batteries, but basically they are only normal lead acid batteries.
the better the battery, lead wise, the better handling of higher voltages.
you need a higher voltage to charge a battery.

so a good lead acid battery/ leisure is needed, as it can handle the higher voltages.

deepcylce batteries, i do not know if they can handle the higher voltages.

in any case, outboard engines only run to about 6500 rpm

please do some reading here:
they do differ from me, but we all can learn from it.

https://www.glen-l.com/phpBB2/viewtopic.php?t=9686

http://www.marineengine.com/boat-forum/ ... ch-voltage

my take on it.
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Re: Mariner outboard overcharging ??

Postby willem wikkel spies » Tue Mar 13, 2018 9:15 pm

and then there is a exciter circuit.......

if no battery is connected, then no charge will take place.
connect a battery on the terminals and charging will take place.

think they call them exciters.......my gat af gesukkel tot ek dit verstaan het.
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Re: Mariner outboard overcharging ??

Postby trier » Wed Mar 14, 2018 6:46 am

I also have an outboard that only has a rectifier, so that the voltage does go up to 16V as the speed increases (on terminals and on plotter). This high voltage has not presented a problem to the plotter/sounder or nav lights but some radios may not like the high voltage and shut down. Fortunately there are ways around that.

The only way to know is to check your outboard for a regulator or the workshop manual. (i have seen on the net universal regulators for outboards)
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Re: Mariner outboard overcharging ??

Postby De Wa » Wed Mar 14, 2018 9:00 am

Hi Guys thanks for all the advice.

I only became aware of the higher charging rate on my last trip when I saw the voltage being shown on my Fish finder.

This may not be something new and could have been the case all along , just that I have now noticed it, I wanted to be caucious

and get advice before going to the water again to prevent damage.

So am I correct in understanding that this higher charging rate which increases with higher revs is normal for a motor with a rectifier?

I just want peace of mind knowing that I will not cause any damage and have a breakdown and get stranded. Don`t want be be embarassed by having to call for help

in the event of a breakdown.

Thanks, De Wa
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Re: Mariner outboard overcharging ??

Postby Pugwash » Wed Mar 14, 2018 9:12 am

At 16v, when the battery is fully charged, you will get excessive gassification. You will need to top up distilled water more regularly but there is also the chance of the battery exploding if the gas can't escape fast enough through the vents. I have personally witnessed the aftermath of a car battery that exploded. It's messy.

Ideal voltage is 13.8v. Rather take it to an auto electrician (or someone in the know) to test it and get it right.
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