Aftermarket Voltage Regulator for 1987 Mercury Engine

Electrical and electronic topics for small boats
MarkCz
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Joined: Sat Jan 27, 2018 3:44 pm

Aftermarket Voltage Regulator for 1987 Mercury Engine

Postby MarkCz » Sun Jan 28, 2018 2:57 pm

I have a 1987 Montauk with a 1987 Mercury 70-HP two-stroke-power-cycle engine. This particular engine only has a rectifier that converts the stator output to DC. There is no regulator, and as the engine run faster than 2500-RPM, the voltage can rise to over 15.6 volts. My Raymarine Dragonfly GPS sonar has an auto shut-off if the voltage goes over 15.6 volts, so periodically my GPS-SONAR unit will shut down. I am using a traditional vented, flooded, lead-acid marine battery and understand that in these old systems the higher voltage going to the battery can cause some of the battery water to boil off so checking the battery electrolyte level is important.

I did a search and saw that I can get a combination rectifier-regulator from CDI that gets installed in the engine, but I like the present simple rectifier for the battery charging.

Has anyone added an in-line voltage regulator to lower just the voltage going to electronics down below my cutoff of 15.6 volts?

I link to one below that would seem big enough to power both the GPS-SONAR and a VHF radio. Do these voltage regulators draw any current when the electronics are powered off? I do have a battery disconnect. Any input would be appreciated.


https://www.amazon.com/KNACRO-Convert-S ... ulator+12v

Long time reader but first time starting a thread.

Jefecinco
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Re: after market Voltage regulator needed for GPS/sonar over voltage problems

Postby Jefecinco » Sun Jan 28, 2018 7:06 pm

An option for your Dragonfly could be a dual battery set up, with one battery dedicated to house power for your electronics, and the other reserved for starting. By isolating the house battery your electronics would be protected from high voltage. Battery charging could take place when your Dragonfly was not needed or with a charger after your outing. It's probably a good idea to keep track of your battery electrolyte level often when charging voltage is higher than a regulated system would provide.
Butch

jimh
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Re: Aftermarket Voltage Regulator for GPS/SONAR Over-voltage

Postby jimh » Mon Jan 29, 2018 11:33 am

I don't have any experience with the "KNACRO DC-DC Convert" in the linked page, but it looks like it would be a good choice for the intended use.

I don't know for certain what behavior is exhibits when there is no load current being drawn, but I suspect the following:

--because the device advertises very high efficiency of voltage conversion (over 90-percent efficient), I infer it is not a simple shunt regulator and must be some type of active, switching regulator circuit; a further indicator is the device is described as a "DC-DC Convert[or]" which strongly implies an active device; the device will be active anytime power is applied to it; an active device by nature consumes some electrical power; there is likely to be some quiescent current, the current drawn when nothing is happening;

--any devices that has less than 100-percent efficiency must, by definition, consume some of the power applied to it in its own operation

On the basis of those two assumptions, I would infer that the device will probably consume some small amount of current even if no output current is being provided. But I don't find that to be unusual. Indeed, I don't think you could find any regulator that wouldn't behave like that.

The simple remedy to having some parasitic drain on the battery by this regulator is to switch it out of the circuit when the downstream devices are not being operated. Just put a switch in the battery positive lead to the regulator--and probably a fuse or circuit breaker, too.

My actual recommendation: buy the CDI aftermarket rectifier regulator. It is a better solution and will avoid over-charging the battery.

MarkCz
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Re: Aftermarket Voltage Regulator for GPS/SONAR Over-voltage

Postby MarkCz » Sat Mar 03, 2018 12:50 pm

I found a 9-Ampere rectifier-regulator kit that has all the parts needed including wiring harness, terminal block that replaces the old rectifier, heat sink mounting plate and the rectifier-regulator at a great price of $50. I hope that will fix the over-voltage.I will post an update after the installation.

MarkCz
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Re: Aftermarket Voltage Regulator for GPS/SONAR Over-voltage

Postby MarkCz » Wed Apr 25, 2018 1:14 pm

This is an update. I removed the old rectifier and installed the new 9-Ampere voltage regulator-rectifier on the outboard. The hardest part of the installation was routing the wiring harness behind the oil tank. The new regulator works like a charm, and my GPS receiver did not shut off at all at higher engine RPM like it used to.

jimh
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Re: Aftermarket Voltage Regulator for GPS/SONAR Over-voltage

Postby jimh » Wed Apr 25, 2018 1:26 pm

DId you buy the CDI rectifier-regulator I mentioned in my earlier reply?

MarkCz
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Re: Aftermarket Voltage Regulator for GPS/SONAR Over-voltage

Postby MarkCz » Wed Apr 25, 2018 2:11 pm

I bought a complete 9-Ampere conversion kit made by Mercury-Quicksilver. The kit was manufactured in 2006. The regulator-rectifier looks to be the same design as the CDI units but there is no schematic to compare. If it fails I will replace with a CDI unit in the future.