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JP Cycles has a 12V, 10A regulator that should work with your OMC generator. I bought one and bench tested it with a Prestolite 4008M generator and 3A load plus battery. The test showed the solid state voltage regulator kept the voltage around 14.5 volts and was constant as the load was turned on and off as well as disconnecting the battery:
P/N 381-309
$44.99
When I put a generator on my 1960 40Hp Johnson I bought a mechanical regulator and was VERY unhappy with it! It would not stay in regulation, sometimes not charging and sometimes +16V. At that time I did not know about the Harley regulator and bought a solid state regulator from a company called Jimcotest that was for a 12V, 10A generator. I never had a problem in over 10 years! However Jimcotest stopped making solid state voltage regulators for generators. That is why I bench tested the regulator from JP cycles just in case I need a spare.
One thing to be aware of when using a solid state regulator is the generator output will require a slightly higher RPM than when using a mechanical regulator. A mechanical regulator holds the field to hard ground at low RPMs. As soon as the generator starts spinning it is building up voltage until the terminal voltage is reached.
A solid state regulator uses a transistor to ground the field and thus requires a slightly higher RPM to get enough current thru the field to excite the transistor to turn on and ground the field. There is also approximately a 2V drop across the transistor which does not allow full generator voltage across the field at low RPMs. I have no idea what RPM this is and I would suspect you will not even notice this subtle difference.
My boat is a heavy 1960 16’ MFG and I have a voltmeter and ammeter on the dash. The only measure I have is that at a slightly higher RPM that would make you a little uncomfortable in a no-wake zone the generator output is up to 14.5V. Since I don’t have a tach I can’t tell you the RPM at that speed. However at cruise RPM up it works great! I highly recommend not even fooling around with a mechanical voltage regulator.
I did not mount my regulator in the solenoid box and chose to mount it under the rear seat and wire it back to the solenoid box. This way it would have adequate air around it for cooling plus be out of the way. The solid state voltage regulators are a sealed unit so there is no concern about them being exposed to the high humidity environment. Just make all your wiring connections soldered or sealed with heat shrink.
Just a little more information……
OMC always used what is called a 3 unit mechanical regulator:
– One unit isolates the battery from the generator so the battery does not discharge into the generator at low RPMs
– One unit controls the voltage regulation
– One unit current limits the generator output to 10 amps to protect the generator. A condition that would be encountered typically with a partially or dead battery.
Some people in the day would use a voltage regulator from a car. This would work fine except car generators were typically 30 or 40 amps. The unit that protects the generator is set to 30 or 40 amps and would provide no protection for a 10 amp generator.
Mechanical regulators also use metal contacts for all the functions. It is also a careful balance of spring pressure, magnetic forces, etc., to work properly. Contacts eventually pit and need cleaning and tension adjustments on the springs need tweaking periodically. In their day it was all they had and it worked provided you did the periodic maintenance.
Dollar for dollar and reliability you can’t beat a solid state voltage regulator.
One more thing, you still need to “flash” the generator if it has been idle for a while and always good practice when installing a new regulator. If you don’t know what that is or why just ask.