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  1. #1
    Join Date
    Mar 2010
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    Karlstad, MN,
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    Default Twin 40 HP Yamaha question

    I tested the boat out for the first time since I bought it. I added a voltmeter to it and the motor connected to it reads 16.2 at WOT. I can't find anywhere that sells a voltage regulator for these motors(1985 ELTK 40 hp). So, can I put both motors on the same battery and disconnect the lighting coil wires going to the rectifier so I am only running one rectifier to charge a battery and then use the other battery as a stand alone unit...no motor connection, for my sensitive electronics?

    If I can do this, can I still get my tach to work if I just disconnect the wires heading to the rectifier?

    OR....can someone help me figure a way to add a voltage regulator. I am not afraid of learning a new skill, have access to plate aluminum and know how to TIG and solder.

    I am not running a maintenance free battery. I can add water, but am worried about the Helix 7 I have getting fried. That being said, I was using a 1977 Johnson 55 for 3 years, probably in blissful ignorance of the overcharging issue. My last starting battery lasted 8 years.

    Thanks.

  2. #2

    Default Re: Twin 40 HP Yamaha question

    Why do you feel the need for a regulator? The current output from your lighting coil is so low that 16.2 volts is not going to harm your battery.

    Or is the problem that 16.2 volts is causing your electronics to shut down?

    Almost any motorcycle permanent magnet generator rectifier/regulator should work. For instance

    https://www.google.com/search?q=moto...26964993993863

    https://www.ebay.com/p/6660123-SPI-0...d=312452681103

  3. #3
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    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by boscoe View Post
    Why do you feel the need for a regulator? The current output from your lighting coil is so low that 16.2 volts is not going to harm your battery.

    Or is the problem that 16.2 volts is causing your electronics to shut down?

    Almost any motorcycle permanent magnet generator rectifier/regulator should work. For instance

    https://www.google.com/search?q=moto...26964993993863

    https://www.ebay.com/p/6660123-SPI-0...d=312452681103

    I am worried that I would damage my electronics. They have never shut down or acted strangely, but until now, I never realized the older engines have no voltage regulator. Electricity is my weakest area of understanding as to how too many volts would affect my more expensive(at least to me) electronics. If it won't affect it, then I won't do anything. These are my first yamahas, but also my newest motors in my boating/fishing career. :-)
    Last edited by bama; 05-08-2019 at 10:04 PM.

  4. #4

    Default Re: Twin 40 HP Yamaha question

    I'm not sure i would add a regulator for 16V, but it is higher than the normal 14-14.5 charging voltage of larger systems

    Your electronics should specific an allowable voltage range, for example, my Lowrance GPS/Fishfinder allows 10-17 VDC. If you are outside of what your equipment is rated for, I would consider the regulator.

    Terry

  5. #5
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    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by tdrudd87 View Post
    I'm not sure i would add a regulator for 16V, but it is higher than the normal 14-14.5 charging voltage of larger systems

    Your electronics should specific an allowable voltage range, for example, my Lowrance GPS/Fishfinder allows 10-17 VDC. If you are outside of what your equipment is rated for, I would consider the regulator.

    Terry
    I took it out today and it went over 17 at WOT. I will check my Helix 7 voltage range. I don't mind putting in a regulator, but mine has a lot more wires than the links posted by boscoe. I am mostly worried about messing up and breaking something else. I never worried before I installed a voltmeter in the dash on this boat and I think it was possible that my last motor was putting out a lot of volts. Sometimes, knowing about something makes it more likely to break.

  6. #6
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    Default Re: Twin 40 HP Yamaha question

    I looked it up and it takes from 10-20V input power. So, I think I am safe. Whew! I just need to make sure I don't buy maintenance free batteries when I need to buy batteries.

  7. #7

    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by bama View Post
    I looked it up and it takes from 10-20V input power. So, I think I am safe. Whew! I just need to make sure I don't buy maintenance free batteries when I need to buy batteries.
    ??? ???

  8. #8

    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by bama View Post
    I took it out today and it went over 17 at WOT. I will check my Helix 7 voltage range. I don't mind putting in a regulator, but mine has a lot more wires than the links posted by boscoe. I am mostly worried about messing up and breaking something else. I never worried before I installed a voltmeter in the dash on this boat and I think it was possible that my last motor was putting out a lot of volts. Sometimes, knowing about something makes it more likely to break.
    Your lighting coil has but two wires. Both green. Two wires into the rectifier/regulator and two wires (one black, one red) out.

  9. #9
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    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by boscoe View Post
    Your lighting coil has but two wires. Both green. Two wires into the rectifier/regulator and two wires (one black, one red) out.
    Yes, but what about the other wires on the rectifier? I would assume I leave the one that sends the AC signal to the tach plugged in from the lighting coil. But, there are several wires coming out of my rectifier that I don't know what they do. I am assuming this is the rectifier. Click image for larger version. 

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  10. #10

    Default Re: Twin 40 HP Yamaha question

    Here is what the rectifier looks like.

  11. #11
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    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by boscoe View Post
    Here is what the rectifier looks like.
    boscoe....you are very patient and I thank you for it. I completely understand what you are saying now. I very much appreciate it!

  12. #12
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    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by bama View Post
    boscoe....you are very patient and I thank you for it. I completely understand what you are saying now. I very much appreciate it!
    I ordered 2 of the rectifier/regulators that you gave me a link for. Thanks, again.

  13. #13

    Default Re: Twin 40 HP Yamaha question

    I have had exactly the same concerns about my 2007 40 XWT. WOT sees about 16volts on my dash voltmeter, confirmed with an external meter. That really is too much for most electronics and globes etc. I found a service manual so that I could do some checks and was a bit surprised to see that the specs quote the following voltages. Cranking 3.5 Volts, 1500 rpm 13 Volts, 3500 rpm 30 volts. This is out of the rectifier, being the black and red wires. I know lots about 4stroke/car systems and electronics is my profession, but still coming up to speed on 2 strokes and magnetos. These voltages just seem crazy and i am surprised that any electronics survive. The comment about maintenance free batteries is valid, they will be damaged by these voltages compared to ones that you can simply top up with water. I plan to do some more research on this but will appreciate comments and input to enlighten me as to how we get away (and we certainly seem to) with such voltages. It seems very odd to me that the output is not regulated.

  14. #14

    Default Re: Twin 40 HP Yamaha question

    Another thing to consider especially if considering fitting a regulator as suggested by bama ,is that 12 volts is also incorrect for battery charging. During charging up to around 14.5 volts is fine (this figure is less for a sealed maintenance free version, a battery will sit at around 12.6 when fully charged. Many of the ebay regulators simply quote the output at 12 volts, this is not really going to get the job done.

  15. #15

    Default Re: Twin 40 HP Yamaha question

    Sorry about multiple posts, but I am researching this on the fly. I see that there are many threads over a lot of years on this topic and the bottom line is that certain of the yamaha models( I am new to the brand) have rectifiers only and no regulator. Is there typically a plug in yamaha rectifier/regulator that can solve this problem or do we need to go aftermarket? I am also getting the impression that for most of the time we just get away with it. Shame to find out that we cannot always get away with it when some electronics is fried.

  16. #16

    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by cellmate2121 View Post
    I have had exactly the same concerns about my 2007 40 XWT. WOT sees about 16volts on my dash voltmeter, confirmed with an external meter. That really is too much for most electronics and globes etc. I found a service manual so that I could do some checks and was a bit surprised to see that the specs quote the following voltages. Cranking 3.5 Volts, 1500 rpm 13 Volts, 3500 rpm 30 volts. This is out of the rectifier, being the black and red wires. I know lots about 4stroke/car systems and electronics is my profession, but still coming up to speed on 2 strokes and magnetos. These voltages just seem crazy and i am surprised that any electronics survive. The comment about maintenance free batteries is valid, they will be damaged by these voltages compared to ones that you can simply top up with water. I plan to do some more research on this but will appreciate comments and input to enlighten me as to how we get away (and we certainly seem to) with such voltages. It seems very odd to me that the output is not regulated.
    What service manual and what page of the service manual lists the voltages you are mentioning? I suspect that you are confusing a charge coil output voltage with a lighting coil output voltage.

  17. #17

    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by cellmate2121 View Post
    Another thing to consider especially if considering fitting a regulator as suggested by bama ,is that 12 volts is also incorrect for battery charging. During charging up to around 14.5 volts is fine (this figure is less for a sealed maintenance free version, a battery will sit at around 12.6 when fully charged. Many of the ebay regulators simply quote the output at 12 volts, this is not really going to get the job done.
    The regulators are nominally stated as 12 volts. Part of a 12 volt system. The R/R actually output nominally 14.5 ~ 16 volts.

    There is more to electricity than voltage. There is also current. In the smaller Yams even though the voltage appears to be high the current is minuscule. Not enough to harm a lead acid battery. Flooded, maintenance free flooded or AGM type.

  18. #18
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    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by boscoe View Post
    The regulators are nominally stated as 12 volts. Part of a 12 volt system. The R/R actually output nominally 14.5 ~ 16 volts.

    There is more to electricity than voltage. There is also current. In the smaller Yams even though the voltage appears to be high the current is minuscule. Not enough to harm a lead acid battery. Flooded, maintenance free flooded or AGM type.

    Hi boscoe,
    I got the regulators and will put them on this weekend. I was hoping I could ask one more electrical question. Since I have the twin 40hp engines, I have 2 batteries...one for each motor. Is it possible to run both motors off of one battery or would the double charging mess the battery or the charging system up?

  19. #19

    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by bama View Post
    Hi boscoe,
    I got the regulators and will put them on this weekend. I was hoping I could ask one more electrical question. Since I have the twin 40hp engines, I have 2 batteries...one for each motor. Is it possible to run both motors off of one battery or would the double charging mess the battery or the charging system up?
    You can do what you suggest. Run both motors with but one battery connected. Unconventional but not impossible. Not sure why you would want to but...

    With the motors running current is coming out of the regulators. The way that the regulators are designed prevents current from flowing back through the regulator to the motor.

  20. #20
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    Default Re: Twin 40 HP Yamaha question

    Quote Originally Posted by boscoe View Post
    You can do what you suggest. Run both motors with but one battery connected. Unconventional but not impossible. Not sure why you would want to but...

    With the motors running current is coming out of the regulators. The way that the regulators are designed prevents current from flowing back through the regulator to the motor.

    I don't plan on it, but was more curious as to if it could be done. I now know that if I had a battery that died on me, that I could add the other motor leads to the one battery to get both motors to work...to get me home.

    Brad

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