charging problems with mercruiser 120 2.5ltr

[catpro1970]

cant find problem with alternater just put it on new now wont shut off with key and when i do turn key off it stays runnin and tach reads max also does volt gauge if i unhook red wire it will shut down ok despertly need advise

 

[Don S]

Re: charging problems with mercruiser 120 2.5ltr

What alternator did you install on it?

 

[catpro1970]

Re: charging problems with mercruiser 120 2.5ltr

i had the parts store match it up with old one also do these 2.5s have internal regulater or external thanks for the reply been going crazy troubleshootin this problem

 

[Bt Doctur]

Re: charging problems with mercruiser 120 2.5ltr

GM 3-wire -internal<br />Mando 3 wire -external<br />motorola 2039 55A<br />Should be one of these. if its a 3 wire, it sounds like you have the 2 wires from the reg. reversed allowing it to supply voltage back thru itself.

 

[tommays]

Re: charging problems with mercruiser 120 2.5ltr

i hope they got you a MARINE one and not a car one <br /><br />tommays

 

[Bt Doctur]

Re: charging problems with mercruiser 120 2.5ltr

Funny how many forget "spark arrested or explosion proof" untill they get blown up and find out the insurance wont cover the damage due to "non-marine parts installed"

 

[catpro1970]

Re: charging problems with mercruiser 120 2.5ltr

the alternater has one orenge main wire one black, then a red and a white coming from a plug at 9o,clock the alternater they gave me was a 78amp alt went and got a 63amp. put it on but havent had a chance to try yet. they told me the red one supplys 12volt to reg and the white one charges the battery. also does anyone know where the orenge wire that comes out dorn at the starter go,s it has a little box on the end of it with a bracket for a bolt it don,t go on the starter or is it a ground thanks for all the help if i can answer anything let me know pretty good with engine stuff just dumb as a rock with wireing

 

[Bt Doctur]

Re: charging problems with mercruiser 120 2.5ltr

That bracket with the orange wire should be bolted to the main battery lug on the starter.The 2 wires you refer to are a "sense lead", and "exciter".If these 2 are reversed, it will back feed power to the ign. circuit and prevent you from shutting it off with the key.

 

[Don S]

Re: charging problems with mercruiser 120 2.5ltr

That "Bracket" with the orange wire you talk about is actually a 90amp fuse. If it's bad, you will keep blowing alternators. From the sounds of things, you haven't wired it correctly (Luckily) and therefore the alternator will still work.<br />I sure wouldn't use the people that sold you the alternator as info on how to hook it up.<br />What year is this engine anyway?

 

[catpro1970]

Re: charging problems with mercruiser 120 2.5ltr

thanks guys on the advise it was that the wires were backwards. it runs and charges like a dream now if i can sneak off to the lake without the little woman it will be a dream thanks agian for all the input. lost n found in ohio