Merc/Mariner voltage problems

[6x6TRex]

I have a 86 Merc 150 Blackmax outboard with an 87 Mariner 150 powerhead on it. I took the boat out today after I finished replacing the water pump and adding a temp gauge. I ran from idle to around 3500-4000 rpms with no problems, then when I approached wot the battery gauge pegged to max and the temp/oil alarm started beeping weird. I brought the motor immediately back to idle and everything appeared fine but as soon as I went above 2000 rpms the battery gauge pegged. I think the voltage regulator went bad. I have the voltage regulator from the Merc powerhead I replaced that I can swap in, or is it something else?

 

[6x6TRex]

Re: Merc/Mariner voltage problems

I swapped the voltage regulator with the one from the merc and it still pegs the voltmeter when I go above 2000 rpms. I have a carquest battery out of my brothers truck right now cause the marine battery that was in it finally died (it was from 02). Is this the cause of my overcharging problems? I wouldn't think the type of battery would matter, I am going to put a marine battery back in it but I would like to use the boat before then!

 

[Laddies]

Re: Merc/Mariner voltage problems

A small battery or bad connection in the system could cause the problem also both engines you mention came with rectifiers not regulators But ovet the years some have had the 9 amp stators replaced with the 16 amp without the rectifier being change outand that will also cause your problem. So if the battery don't help it and the connections are good and you have a rectifier (4 wires) you may have to change to a regulator (5 wires)