Alternator

noidea44

Hi Everyone-
I have a 2011 Rinker 246 with a merc 350 mag and it’s time to replace the alternator. I read many posts about alternators and I am torn between switching to high output (105amp) or keep the stock (70amp).  I have two group 27 batteries, a 1000 watt stereo amp (which I assume draws a lot of amps), Ocean led under water lights and a garmin gps.

It’s my understanding the stereo amp is drawing most of the power. Some posts  I read says to go with the high output and other say stick with the 70amp. My decision is not based on money but rather will I do any damage with the output alternator or do I need to upgrade any wires or breakers if I go with the 105amp?

LaRea

Most express cruisers don't bother with high-capacity alternators.  You'd probably need to upgrade the wiring and the battery isolator.  And unless you're living the wakeboarding lifestyle, you probably won't be pumping a kilowatt of music while you are underway, so you won't need the extra current.  

For what it's worth, I just installed two API Marine alternators that seem to be high-quality stuff.  I went with the 70-amp model.  

Handymans342

The alternator output at 105 wont hurt anything but does nothing for you if you are just sitting

69fastback

Using ohms law, a 1000 watt amp only needs a 75 amp alternator, but that’s assuming nothing else is drawing off of the system. Given that the boat needs a 70 amp alternator, and you need 75 for the stereo alone (at 13.5V), I would definitely install a higher output alternator. No need to worry about fuses, breakers, or wiring to other components. It’s important to understand that amps are on a “as needed” basis, and electricity takes to path of least resistance, so there will not be an increase in voltage, or amps, traveling to other components. Your amplifier will draw more amps, and you alternator will be able to provide, and since it’s path of least resistance, no other components will see an increase in amps, which in turn, will not affect anything else. 

You will want to upgrade you grounds, and battery cables to handle the extra output, and that’s it. I have a 230 amp alternator in my boat, with nothing more than upgraded grounds, and battery cables, and all is well. No blown fuses or tripped circuit breakers.

69fastback

Alswagg said:

69 the 246 does have a 90 amp charging circuit breaker on the alternator output wire     All of the newer designs have this.  If it has a dual battery system, there is also a 90 amp breaker at the selector switch panel   All of this is prior to the battery.     The only times we see these trip are when one battery is flat dead and the 2nd battery is used to start the boat and then switched back to the dead battery to charge up.     It’s rare. It happens usually after setting all day at a sand bar or overnight 

I can see how that would be different. The only circuit breaker I’ve ever seen on mine, is on top of the engine, for the ECU.