High charging voltage - 50HP 2 stroke

[CharlieK1988]

When I run my motor at 1/2 to full throttle the voltage meter reads 14 to 16 volts. Is there a voltage regulator on the motor or what else could be causing the problem? I'm afraid of ruining my new battery...
Thanks!!!

[Hamfisted]

If you're just going by what the gauge on your dash reads I would connect a quality digital multimeter to the harness and get a reading from that, rather than trust the dash gauge. They are not too reliable. Connect the multimeter to the battery terminals and see what kind of voltage you're getting there at those throttle settings. But yes there's a voltage regulator if it ends up being a problem.


Mike.......... Miami, FL

[Ken]

Charlie,
You can calibrate your console gauge by using a (quality) voltmeter just like Mike suggests.
The charger/regulator of your motor should charge your starting battery up to a max of about 14.5 volts. At idle, the regulator should be putting out around 12.5, and increase to 14.5 as the motor increases rpm up to mid-range and beyond.
This assumes a battery that is in good shape, i.e., one that will accept a full charge.
On my boat, when I first crank up, my console voltmeter (I calibrated it with a digital voltmeter) reads about 12.5 at idle. When I get up on plane, the meter will read around 13.5, and after a few minutes, when the battery is fully charged, the meter will read 14.6 volts.
Hope this helps [img]smile.gif[/img] ,
Ken K

[CharlieK1988]

Thanks for the advice. The boat came with a new battery. I checked the voltage with a Fluke voltmeter at the battery with the motor running at about 3500 RPM. It was 16 volts. Also my fishfinder shuts down with an error message "voltage too high" It is rated at 15 volts max. I can put a resistor on the plus side of the fishfinder to drop the voltage, but I still worry about the battery getting overcharged. Maybe I'll try putting my other battery in and see if that cures the problem. I see no voltage regulator in the schematic for the motor. Just the diodes which check out good...
Thanks again.

[boats.net]

You need to have the battery tested, load test and check with hydrometer to see if has a bad cell. Check to see if battery cables at battery and engine are tight and clean, check all wire connections on engine make sure tight. If all thats ok then replace voltage regulator.

[Ken]

Charlie,
Your Fluke voltmeter and your fishfinder are telling you the voltage from the regulator is too high - I would replace it.
Ken K [img]smile.gif[/img]

[CharlieK1988]

Where is the voltage regulator? I don't see it on the schematic. The diodes go directly to the battery through a 10 amp fuse. Is there a voltage regulator available aftermarket? This is a 1987 50 HP 2 stroke
Thanks again for all your help.

[boats.net]

Go to http://www.boats.net/yamaha/partsyst...53641a85bd1d80
and the regulator is reference #5.

[Ken]

boats.net,
Item #5 is listed as a "rectifier assembly" - is the regulator built into it?
Ken K

[CharlieK1988]

Hi Ken,
Yes, it is a full wave rectifier not a voltage regulator. Mine ohms out good. An extra one came with the boat so I think the previous owner changed might have changed it because of the high voltage. I found some regulators on line but they are pricy. This weekend I'm going to put my other battery in and see if it makes a difference. Maybe the battery is bad, although it's fairly new.
I really appreciate your feedback. Thanks again...
Charlie

[Ken]

Charlie,
A "bad" battery is not going to cause an over voltage condition like you are experiencing. I suspect you are getting the raw full-wave rectified voltage out of the bridge rectifier, and you need to put a regulator between the rectifier and the battery.
I would start looking at the motor diagrams in the online catalog for each year up from yours for the 50 hp to see the first one that was available with a regulator. You may have to make some kind of bracket to hold it - a custom installation. Or you could mount the regulator somewhere close to the battery.
Good luck [img]smile.gif[/img] ,
Ken K

[CharlieK1988]

Hi Ken,
I beleive you're right. I pulled out the "new" battery that came with the boat and it was really low on electrolite. A good indication of over charging! The battery measures 13.3 volts without a load...
I'll look for an upgrade from Yamaha or get a regulator from another marine engine. I think Mercury has one that will work...

As always thanks.

[CharlieK1988]

Hi Ken,
Found a rectifier/regulator!
(1996 Yamaha 50) Should do the trick.
Also putting a small 12 volt inline regulator
on my electronics, lights, etc. Will leave the voltage gauge connected to the main power line so I know whats going to the battery.
You've been a great help!
Chuck

[Ken]

Chuck,
I believe all you need is the inline regulator, because you already have the rectifier on the motor - right?
If you feed the full-wave bridge rectifier signal to another rectifier, you won't get anything out of the second rectifier.
Just make sure the inline regulator is rated for the proper current - probably for your motor is going to be about 10 amp (my C115 is 20 amp),
and, of course, 12 volts.
Good luck, and let us know how you come out [img]smile.gif[/img] ,
Ken K

[CharlieK1988]

Hi Ken,
I noticed that blake115Yami has the same problem. I responded to his question with my latest findings. You might find it interesting that after I dicharged the battery some it charged normally. Not sure what this means but all looks good so far. Check his forum for my response.