voltage regulator/rectifier

[rbreaux]

1996 mercury 2.5L FF block was EFI, removed and made a Carbbed motor....turn 6500 regulary, somewhat race stuff....the serial number was for the EFI set up orginally...It has a 16amp charging sysytem....I need help locationg below problem! GO ......Thanks in advance....

So I've changed 3-4 rectifiers......dead battery first one, changed tach on the second one only to figure it was not the tach that was bad....Then did change the bad tach and another rectifier.....its been 2 months and now my volt meter on the boat will go from charged and starts everytime, but fluctuates from below 12 to pegged out to 16volts while running.....I do have an amp on the radio, turn radio/amp off and no change to volts...turn motor off and the meter will read 12.5-13 volts....what is making the spike

[JOE54]

suspect regulator

[leonreno]

Are you using Mercury regulators or aftermarket regulators? If aftermarket, which brand?

Also, what type of battery are you using? Should only be a wet cell starting battery that is not maintenance free.

[rbreaux]

I’ve used both OEM and aftermarket (Napa brand). They seem to do fine for a time or two and then start to spike again.

[leonreno]

What battery are you using? I would also check all wire connections for looseness and corrosion. Connections at the battery and on the motor. Also the connections of the regulators. Pull apart and make sure they aren’t burnt up.

[rbreaux]

Leonreno, could it be too small if a battery (750) drawing too many amps when radio/amplifier are on getting the rectifier too hot and burning one side. All connections are and clean and new. I did have a 950amp battery when it died I didn’t think I needed so much for a carbed motor

[EuropeanAM]

Let's clarify since you're using a non-standard charging system:

Are you indeed using only a Block RECTIFIER? If so, it has no capability to limit voltage (only to rectify the AC output to DC).

Though not the originally intended installation, I'd be using an OEM late-style REGULATOR that is fuse-circuit protected, has redundant grounds, and should be capable of up to 20 amps (that's 1/2 of the stock 40a charging system used on the later 2.5 Laser-Style EFI's).

Lead-Acid battery only (no maintenance free, Deep Cycle, AGM, or Lithium).

[lpugh]

I would get rid of the radio and amp as that would pull the battery state of down reducing the charge resistance which could add to problems with a stator system. If you keep it, connect to house AGM or lithium that in no way be connected to the starting battery.

[rbreaux]

European AM, thanks for responding. I know it’s a 16amp system, lead acid battery and the rectifier if I may draw a picture; resembles 2 triangles together with 3 posts to attach the wires. IMG_4625.jpeg

[massbays]

The original charging ckt on that motor did have that overcharging problem and it was a regulator.
it would charge @ 16+v, EFI electric fuel pump would quit.customer would paddle back to dock,
by this time battery voltage has fallen back into the 12v range.Hit the key and motor restarts.
go back out 16v,motor quits,paddle back to dock.
Took a while to figure that one out.

[EuropeanAM]

I'd look into installing one of the 8M0084173 Regulators. Would need a suitable mounting location, and the stator/power/tach wiring would need to be configured with OEM Bullet Connectors to match the regulator. That regulator is rated for 20 amps so it should be more than capable of doing the job (in theory).

[rbreaux]

Thanks European AM, I will look into the regulator you suggested...

[chad202]

With my modded 260, the regulator always acted weird and did stupid stuff. I ended up removing it and it ran flawlessly. I read voltage on an analog gauge as well as my GPS unit and while running when if it would get to 14.5(mainly in the morning battery was freshly changed), if my radio wasn't on, I'd turn it on. If that wasn't enough to get the voltage in control, I would turn on the navigation lights and that always did it. Once I swithed to the Brucato ACU, I never worried about it since they could withstand more voltage than the merc ECU. Not recommended any of this, just letting you know how I did it.

[rbreaux]

With my modded 260, the regulator always acted weird and did stupid stuff. I ended up removing it and it ran flawlessly. I read voltage on an analog gauge as well as my GPS unit and while running when if it would get to 14.5(mainly in the morning battery was freshly changed), if my radio wasn't on, I'd turn it on. If that wasn't enough to get the voltage in control, I would turn on the navigation lights and that always did it. Once I swithed to the Brucato ACU, I never worried about it since they could withstand more voltage than the merc ECU. Not recommended any of this, just letting you know how I did it.

So I installed a 20amp regulator as what European suggested and all problems solved. Thanks European.

[leonreno]

That’s great, and thanks for reporting back, helps us all.