Dead Battery

[imported_Lake_Rat]

I have a 1988 merc. 70 HP. on a pontoon. It has been starting easily and seemed to have no problem. The other night I had it out after dark using my nav lights and a fish finder. When I went to start it the next day, it barely turned over. I charge the battery a bit and got it started. I then took the boat out for about 15 mins. and returned to the dock, shut it off and restarted it. It turned slowly but started. The second time no-go. I have a few questions. How does this motor charge a battery? Will the engine run without the battery? what voltage should I see at the battery with the motor running? Thanks for any help.

 

[Barnacle_Bill]

Re: Dead Battery

You have a stator under the flywheel that feed a rectifier, usually with 2 yellow wires. The first to go is the rectifier. If you ever hooked the batter up backwards, even for a split second, the rectifier is probably shot. An easy way to check this is to measure the voltage at the battery. Then start the motor. You won't see much of an increase until around 2k RPM so don't do it with muffs. If you don't see any increase, replace the rectifier.

 

[imported_Lake_Rat]

Re: Dead Battery

Thanks Much!

 

[Laotzu]

Re: Dead Battery

Check the condition of your battery connections, and water level if you can. A corroded ground cable which is common, will keep it from charging correctly.<br /><br />I've seen on this forum many times to not dissconnect your battery with the motor running. Lack of ground will fry a lot of stuff.<br /><br />Jerry

 

[Perfidiajoe]

Re: Dead Battery

also check condition of the battery.