1988 90hp Merc - is alternator working properly?

[etienne]

How can I determine if the alternator on my 1998 90h Merc is working correctly? I don't have enough history with my battery to know if it's being charged properly & wanted to test the alternator itself.

 

[TheChad]

Re: 1988 90hp Merc - is alternator working properly?

Good question.<br /><br />I shal wait with you for one of the 'Experts' to answer <br /><br />-TheChad

 

[Laddies]

Re: 1988 90hp Merc - is alternator working properly?

Connect a voltmeter to your battery, start the engine and run a high idle you should see a raise in battery voltage to 14.5+ volts

 

[etienne]

Re: 1988 90hp Merc - is alternator working properly?

thanks, I'll try it over the weekend & post the results.

 

[Sylvanowner]

Re: 1988 90hp Merc - is alternator working properly?

Do you have a fish finder that has a diagnostic system in the options menu? Usually there is a spot in there that will tell you real-time voltage. You can check the voltage before, during and after start up. Easier than using a seperate voltmeter.

 

[etienne]

Re: 1988 90hp Merc - is alternator working properly?

Good timing Thomas,I just bought a new Humminbird Matrix 17 with that feature. I discovered 12.4 volts under all conditions. What's my next step to determine exactly what needs to be replaced?

 

[andy6374]

Re: 1988 90hp Merc - is alternator working properly?

You probably need a new rectifier. <br /><br />-andy

 

[etienne]

Re: 1988 90hp Merc - is alternator working properly?

thanks, I'll take a meter to it & see.

 

[etienne]

Re: 1988 90hp Merc - is alternator working properly?

Thanks Andy, you were right . . . blown rectifier. I'm going to try the Radio Shack route ($5 Canadian part # 2761185)& bolt to a chunk of aluminum & drill holes to fit the original footprint. Oh ya, thermal grease too.