Alternator replacement - 5.7LX

[drs416]

I want to replace the alternator on my 1996 5.7LX Mercruiser - I'm installing a reman longblock (from Mercruiser). OEM altternator is part # 817119A4, which appears to be 55 amp Mando type. My questions: 1) Can I replace with a 65 amp model (e.g. Sierra #18-5965)? 2) What are advantages/disadvantages of the 65 vs 55 amp? 3) Any advice on manufacturers (Quicksilver, Sierra, Arco, MES, API, Delco)? 4) Any other things I should consider?
-Don S

 

[Don S]

Re: Alternator replacement - 5.7LX

The big thing is how the alternator mounts and the pulley alignment. The wiring is easy to change.
Just find a MARINE alternator with the same mounting and it MAY work.

 

[drs416]

Re: Alternator replacement - 5.7LX

Thanks for the reply. So, everything being equal, is there an advantage of a 65 amp over a 55 amp alternator? And re the wiring changes, do you mean I will need larger gage(ie smaller AWG #) for the 65 amp?

 

[wire2]

Re: Alternator replacement - 5.7LX

.......is there an advantage of a 65 amp over a 55 amp alternator?

Only if you need more than 55 amps to power the ignition and accessories on the boat

And re the wiring changes, do you mean I will need larger gage(ie smaller AWG #) for the 65 amp?

I believe Don is alluding to the difference between 1 wire and 3 wire alternators.
An alternator will try to produce only whatever current is drawn from the battery, to maintain a regulated voltage, nominally 13.8v. It doesn't "force" 65 amps into the system.
Unless you've added a lot of electrical load to the system, your existing wiring will be fine.

 

[DHPMARINE]

Re: Alternator replacement - 5.7LX

That Sierra number is listed by Sierra to replace your Merc number.It should bolt right in and wire right up.

I haven't used Sierra electrical parts as I am satisfied with ARCO.

DHP

 

[thrasher]

Re: Alternator replacement - 5.7LX

The only advantage of a higher output alternator is the ability to run more electrical devices on the boat and to recharge the battery faster!! If you adda second battery to your boat, a larger alternator is also a good idea to allow charging of both batteries.
Your wiring should be fine..

Gary

 

[drs416]

Re: Alternator replacement - 5.7LX

Thanks all for the input. Sounds like there are no disadvantages to the 65 amp (except a little more money) and some advantages that are appealing to me.
-Don (drs416)