Battery?

I recently got my '66 Evinrude 80hp Starflite running and it runs great with the help of some of you on this forum. I appreciate you answering all my questions. I've took a meter reading at the battery while running and it will range from 12.5-16+ I was using an auto battery which I read in some posts that I must use a marine battery which I planned on purchasing once ready to go on the water. I read not to use a maintenance free marine battery. What type of marine battery should I use and what size for my 80hp?
Thanks

Anything 75 amp hour or over would be fine.

The reason for not using a maintenance free or a gel battery is because you have a rectifier only charging system and not a regulator...you can overcharge them and blow the rectifier...there are many theories on why this happens but the one i like best is a regular battery (which you are probably running now) has an internal discharge that happens instead of overcharging..the battery you want is the low aph that is recommended in the owners manual..if i remember correctly that is about 385 aph...you are going to find a quality one hard to find... shoot for a 500....if the auto battery you are running is a good one i think i would just run it...watch the water level in the battery a little closer than you would in a car....one good thing is you do not need the rectifier to run...if it blows the battery will be charged and you have many starts in it to finish the day....

i was typing my answer when yall made your entry kim and joe...sorry about that...one finger slow typer here..

if you dont have a permanent voltmeter i would get one and mount it where you can watch it with this motor..

My '66 service manual calls it a regulator not a rectifier. It's part #380076.
Thanks

Agreed you have a voltage regulator on this motor.----The rectifier / diodes are under that wee black cover up on starboard side of the motor.

Thanks racerone. I did see them when I looked closer at my service manual. It also says how to test them. Can you clarify by using a auto maintenance free battery this could be causing my higher voltage readings? What I'm hearing I should use a wet lead acid marine battery and a starter battery not deep cycle?

if indeed you have a regulator and it is putting out 16 plus volts then it is broke...a maintenance free marine battery is ok to run if you have a regulator...the output should hold steady at 14.8 volts..

I know this is an old post, but I was just noticing when looking for the rectifier part number on this website for my E150STLCOS 1985, that no maintenance free, dy, gel, automotive battery's should be use. So I purchased a 900cca auto battery for my motor because I was having slow start issues. I think Joe is probably familiar with this. So now I am thinking my rectifier might be blown, but this was using a 750deep cycle mca anyway. I am just wondering if I should take my new $150 battery back and keep my DC or just keep it for a spair or run it. I am going out right now to look and see if it is maintenance free to boot, I am thinking a battery that size is not. Ok ya confirmed that it is not a maintenance free battery. Any thoughts? I am already looking at getting a new rectifier. I guess, what I should do is test my voltage while the motor is running. I know a second battery is nice, but this one is like almost 100 pounds, lol

I believe your motor has a regulated charging system, which should control the voltage. I won't get into the battery type issue.

thanks for the response. I have noticed that everything says it is a rectifier/regulator, but I can't find any specs on the the part numbers. If I could find a data sheet that would be great. The parts list says to not use certain types of batteries because of the drain and liquid consumption and weak cores. I am not clear as to what this regulator will do to my new battery. I see that the 10 and 35 amp stators and rugulators are available for my model, so I can't quit figure what I have and how it will impact my battery if it will over charge it. I am looking at building or buying a 12v/1-5amp regulator to just keep the battery charged and maybe splitting off with a separate regulator for my deep cycle to power anything extra, not sure exactly how to do that, but doesn't seem too difficult. Just mostly worried about the new battery getting fried or frying my stator.

Test your voltage while running awhile. If it is about 14.5V, the regulator is working so run what you have and don't make it complicated.

thanks, sounds good to me. I will start the engine tomorrow and test it. I am betting it is blown because I have no tach now and there is something pocking up out of the plastic on the upside of the casing on the regulator. In fact I have no gauges, not sure if that is a wiring problem, but last season and before I started work on it this season I had tach and now suddenly it is gone and the regulator is looking funny