Over charging

[djsly4]

I have a 1988 100 hp Mercury which recently began charging at 16 volts. This has never been an issue in the past so I know it is not suppose to be at this level. I immediately thought that my voltage regulator went bad, but when I went to find it , I could not locate the regulator only the rectifier. After some research, it seems that this 1988 engine is not equiped with a stand alone voltage regulator and just relies on the stator. I am unsure how this works and regulates the charge, but I do know it is not the standard stator, it is a different model number for this stator.
The short question with the long explanation is can i install a separate voltage regulator on this engine? I know there are regulator/rectifiers which can be used on some engines, I am unsure if something like that will work for this one as it never had a regulator on it? Any help is appreciated.

 

[GA_Boater]

The short answer is yes and the long answer is with no regulator the battery acts as the regulator. Check and clean all the battery connections, both ends.

Moving this to the Merc outboard section. Welcome aboard.

 

[merc850]

Don't use a maintenance free or an AGM battery with this system the electrolyte will boil away quickly. However if you want to install a regulator.......
here are the parts; you should be able to buy the regulator at your local Mercury dealer.

 

[djsly4]

Don't use a maintenance free or an AGM battery with this system the electrolyte will boil away quickly. However if you want to install a regulator.......View attachment 352736
here are the parts; you should be able to buy the regulator at your local Mercury dealer.
View attachment 352735

Thank you for the reply, the diagram is great and yes, I am changing batteries to a deep 27. CDI recommended I go with a regulator rectifier and gave me the one they said would work. My only question is one is 5 wire and one is 6. I am trying to figure out which I should use. I know the 6 has one extra wire and it is B- but unsure where that goes if that is the one I use. This system you showed looks really simple so this might just be the answer. I hate to overthink alot of this stuff.

 

[merc850]

Also, deep cycle batteries are not recommended for the motor either, you just need a regular Marine starting battery, the alternator is for keeping the battery "topped up". The 6th wire is probably for grounding.

 

[Dave1027]

OP. Others have correctly answered your question. Just wanted to say I have the same motor and probably boat as you. I see your '88 100 hp Merc has a white cowl. That probably means you have a Searay Seville?

Edit to add. The best battery I have found for this motor is a Walmart EverStart 24MS marine starting battery. It's lasted me many seasons and did not cost very much.

 

[electricjohn]

Keep a close eye on your electrolyte levels too. Especially in cells 1 & 6. I have gotten as many as 13 seasons out of a battery with the same charging set up you had. It was a Sears marine battery.

 

[djsly4]

OP. Others have correctly answered your question. Just wanted to say I have the same motor and probably boat as you. I see your '88 100 hp Merc has a white cowl. That probably means you have a Searay Seville?

Edit to add. The best battery I have found for this motor is a Walmart EverStart 24MS marine starting battery. It's lasted me many seasons and did not cost very much.

I put the new battery in and now it seems to be staying at a lower voltage. Thanks

 

[djsly4]

I put the new battery in and now it seems to be staying at a lower voltage. Thanks

Yes it is a Seville, been a great boat and motor, first issue I have ever had with it