Merc 500 how to test rectifier

[TominatorNY]

Can someone walk me thru how to test the rectifier on my 1969 Merc 500 50 hp? (I know, "get a SELOC manual" - I just ordered it!) I don't think the motor is charging the battery. I get 13 v at the battery terminals when its not running, and 13 volts when it is running, no change. I'd greatly appreciate the help! Thankx.

 

[ronmold]

Re: Merc 500 how to test rectifier

Disconnect battery. Remove the yellow stator wires from the rectifier and check for continuity across the wires. They should show low resistance. If so, stator should be OK. Next put meter on 2K or if it has it, the diode range. check from one of the open recifier lugs to ground then reverse the leads & try again. They should show open one way, closed the other. Do this with the other open lug. Readings should be the same for both posts. Now do the samething but with the + pos post instead of to ground. Readings should be opposite of the "to ground" test. If you get continuity one way and with the leads reversed you have a bad rectifier. Radio Shack has a 25AMP rectifier for around 7 bucks that will work fine if you're handy w/ a solder iron or you can use crimp-on spade lugs. run the yellows to the 2 "~" (AC) terminals and a ground wire to "-" and red to "+". Good luck

 

[phatmanmike]

Re: Merc 500 how to test rectifier

Radio Shack has a 25AMP rectifier for around 7 bucks that will work fine if you're handy w/ a solder iron or you can use crimp-on spade lugs. run the yellows to the 2 "~" (AC) terminals and a ground wire to "-" and red to "+". Good luck<br />

actually its only 3.49, i bought two of them on my last outing. easiest way to check if its charging is measure DC voltage across battery with motor off, should be 12.8 ish . measure same voltage with motor at fast idle, should be more than 13 volts, if not replace that rectifier

 

[ttpsb]

Re: Merc 500 how to test rectifier

hi<br /> im new to boating and sounds like u have the same mercury outboard as me its serial no is 1937802 asim trying to find a book on it <br />is this near the serial no of yours if so it may be the same manual if this is the case where did u get it<br /><br /> TREV

 

[ttpsb]

Re: Merc 500 how to test rectifier

PS mine is a manual start if that helps only got two wiers comeing out of the back of it for battery (thoght there was more) any help <br /><br /> TREV