1987 45hp mariner charging issues

Trapbum · #1 June 29th, 2009, 09:06 PM

I have a 1987 45hp 4 cylinder mariner engine. I noticed that the battery status gauge was showing low life when I was out the other day even when the engine was running. When I got home I hooked up the charger and the gauge pegged so I know the gauge is good. I have verified the rectifier is good. I show zero continuity across the two yellow wires going to the stator. When running I am getting 20vac at idle speed from the stator. When I run the engine I am getting around 12.10 vdc out of the rectifier. I am curious if I have hidden issues. Can anyone assist a fellow fisherman.

Thanks
Trapbum

Pcack51 · #2 July 9th, 2009, 10:51 PM

Boss,

I'm in the same boat. (HAHA) One thing I tried was putting the muffs over the intake and starting the motor with the gear engaged. Check your battery with a volt meter and see if your getting 13V or higher, then maybe your good. On my Mercury 40 the gear has to be engaged to charge the battery? Please advise if tht isn't the case...

emckelvy · #3 July 10th, 2009, 02:44 AM

It sounds like you're getting plenty of AC voltage out of the stator, even at idle. If DC output does not rise when the motor is throttled above idle, the rectifier is shot. You won't get much DC output at idle, however, so if you were trolling for a long time with a bunch of electronic gear going, it'll discharge the battery. The stator is only rated for around 10 amps charging, pretty nominal in any case. And that's at speed, not idling.

You might try picking up one of those El-Cheapo Radio Shack 25-amp-rated bridge rectifiers and just temporarily wiring it into the circuit to see if there's any change from your motor's rectifier. Under $5 and would actually work well enough as either a temporary or permanent replacement.

Just remember that the Rad Shack rectifier has to have its Negative terminal separately grounded, not thru the case as is the stock Merc rectifier.

HTH............ed

Pcack51 · #4 July 20th, 2009, 09:26 PM

I found out my issue... The charging sys only kicks on when your up to 1200 RPM's. So, when I was anchored and running the radio, fish finders and other equipment I had drained the battery enough not to turn the engine over.