Alternator

[ronjon1944]

I have a 1988 3.0 mercruiser. The alternator (merc. 12449((mando))55amp.) is bad.<br />Can I replace it with a higher amp. output alternator (60-70amp). If yes, is there a 3wire one that will fit in the same bracket and use the same belt?<br />Thanks

 

[jlinder]

Re: Alternator

when I replaced mine I went with one from a company called ARCO. Talked to them directly. YOu might want to call them. http://www.arcomarine.com/catalog.htm <br /><br />Question, why do you want more than 55 amp? What do you have that draws a lot of current? <br /><br />On a car we are used to more power - fan, lights, wipers, power windoes, etc. Don't have that on a boat.

 

[MH9371B]

Re: Alternator

I have bought quite a few parts from an ebay retailer.. http://stores.ebay.com/Collectable-Parts_W0QQsspagenameZl2QQtZkm <br /><br />I got a perfectly good alternator from them for $65

 

[Laddies]

Re: Alternator

arco is a first class outfit and I am sure will help full to you

 

[Bt Doctur]

Re: Alternator

Only one illl use is the GM unit.single or 3 wire. I throw mandos away.they seem to have a winding problem at higher rpms and go open internally.amps dont mean that much unlees you go lower than specified and cant charge the battery properly.

 

[jlinder]

Re: Alternator

I was very inmpressed with ARCO. Talked to them about how they make them. Found out that after they hand test each one for electrical/mechanical they then take each one to an anechoic (spelling?) chamber.<br /><br />There they use a computer to listen to the bearings / mechanics to reveal any problems in the making.<br /><br />I believe it. There was a feel to it when I spun it that was real smooth.<br /><br />Bt Doctur - sounds like you have done this for a living. Have you gone through a lot of alternators?<br /><br />ronjon1944 - Sounds like you live only about 20 min from me.

 

[Boatist]

Re: Alternator

RonJon<br />If it is a 3 wire alternator then I belive it has a external regultor which also could be the problem. The one wire units have the regulator built in.<br /><br />another though would be to repair your own unit. Most problems very easy to fix.<br /><br />Bad brushes or Bearings very cheap and caused by lots of hours of use. $4 to $10. <br /><br />Bad diode block or diode triode caused by turning battery switch with motor running, loose or corroded battery cable. $10 to $20.

 

[jlinder]

Re: Alternator

Mine is a 3 wire (1988 also) and has internal regulator. The 3rd wire is for senseing the voltage.

 

[Boatist]

Re: Alternator

Jack L<br />Good to know some 3 wire have an internal regulator. Mine a 1980 has a output wire, a wire back to the Key and a field winding which comes from the external Regulator.<br /><br />Mine is a 35 to 40 amp Alternator. On my boat thinking about wheather I need a higher amp alternator I would say no as when I start up voltage reaches 14 volts in less than 30 seconds. I guess a higher amp could reach 14 volts in 20 seconds but once you reach your regulators voltage then it is just up to the battery to charge and that takes time not more Amps. Checking the spec on mine saw a minumin of 10 amps at 1500 RPMS and 35 amps at 4500 RPMS. Was thinking that is pretty low until I realized it is alternator RPMS not engine rpms. Higher amps with the same belt means the belt must be tighter to prevent slippage while under full load.

 

[jlinder]

Re: Alternator

When I replaced my alternator ARCO had an advisory with it to change the wiring slightly.<br /><br />It said that the 3rd wire coming from the key switch is the sense wire that controls the regulator. This wire runs up all the way up to the ignition key and then back to the engine.<br /><br />On older boats corrosion and the longer run can add resistance to the circuit and mean that the sense voltage is lower than the actual battery boltage.<br /><br />Since the alternator uses this wire to control the voltage, to make the sense voltage correct the alternator can be tricked into putting out a higher than normal voltage to the battery. This can cause overcharging.<br /><br />They reccomend removing the sense wire from the key switch, taping it up, and running a jumper from the alternator output to the sense terminal.<br /><br />I did that and have been happy

 

[ronjon1944]

Re: Alternator

Jack L, Thanks for the info<br />I live in cobb county up close to Woodstock

 

[trog100]

Re: Alternator

u dont need many amps to charge a battery.. the extra amps are only needed to run auxilary equipment at the same time as chargeing your battery.. <br /><br />how big an alternator u need depends entirely on how much auxilary equipment u run..<br /><br />just to get things in perspective.. bigger might seem better but sometimes it just isnt needed and as such is simply a waste of time and money..<br /><br />trog100

 

[ronjon1944]

Re: Alternator

as with JackL, mine is a 3 wire and has internal regulator. The 3rd wire is for senseing the voltage. I'm running with a fishfinder, radio/CD<br />(got to play music for the fish)and lights for night fishing.<br />Talked with ARCO my part is a 60050 55amp but they now have a 65050 75amp $30. more<br />Thanks for the help guys

 

[whywhyzed]

Re: Alternator

More amperage alt. can be a fire hazard. Your output wire, breaker etc. are designed to carry the max current of the original alt. 20 extra amps may or may not be a problem..<br /><br />I put a self exciting regulator in mine to get rid of the excitation circuit. That might be an option from ARCO too you might want to explore. just simplifies the whole wiring deal....makes the 3 wire alt. a "one wire" type ...so you don't have to make up a jumper.