alternator upgrade

trickyricky

I don't think my stock alternator is able to keep up with the increased demand i have put on the system with the stereo upgrades i have done.  Does anyone have any suggestions for upgraded alternator?  I have heard that they have 160 amp altrrnators now but not sure if that is over kill.  

I have a 496 motor with stock alternator but i added two amps with over 3000 watts.

trickyricky

RY, I will look into that.  Thanks for the suggestion. 

Black_Diamond

Just dropping in a big output alternator may not solve your problem, you have to consider your battery amp hrs too, plus the wiring upgrade (potential).  You might need bigger batteries too.  Remember the alternator output rating is when at high rpm, so at idle you get far less power from it.  This is why you see some cars have headlights dim or fans slow down when at idle.

Here's a general rule:  When considering an alternator size you can apply a simple rule: the alternator output in amps multiplied by 4 should match the size of the battery banks in amp hours.  So a 70 amp alternator would work well with a 280 amp hour battery bank.  This is a very general rule so don’t worry if you bank rating exactly.  If your alternator is too big it won’t hurt anything but it may not be able to work at its full potential.  If your alternator is too small it will just take a bit longer to charge the bank fully.

trickyricky

Thanks for all the great advice, that's  why I love this forum.  My mechanic on the other handis not always so thrilled since you guys have helped me call him out on some BS.  

aero3113

trickyricky said:

Thanks for all the great advice, that's  why I love this forum.  My mechanic on the other handis not always so thrilled since you guys have helped me call him out on some BS.  

That's not good if you have to deal with your mechanics BS, maybe you should find a new shop?

trickyricky

Done!  It is hard to find a good mechanic sometimes.

trickyricky

I contacted a local alternator shop, it should be ready at the end of the week.  I also found a new mechanic who was recommended by a couple of fellow boaters in my area.

trickyricky

Alternator was fine and without going to a larger size they were not able to beef it up enough to make a difference (housing on current alternator does not have enough room to bump it to 160 amps).  I only have two batteries and was running the motor off of the same battery that my stereo was hooked up to.  They both charge with the alternator but it was hard to keep up with the demand on one battery.  The guy at the alternator shop told me to run the engine off the opposite battery as the radio and it worked.  My volt gauge read correctly and everything seemed to work much better. 

I am thinking about getting a 3rd battery to run my creature comforts but it is not high on my priority list this late in the season.

Michael T

First, good advice about changing and isolating your batteries. Second, getting a house battery or two imo would be best for your apparent needs. I had 3 house batteries in my 310 and have 3 house batteries in my 360. All of them plus the two starting batteries are series 31 AGM batteries. Last, congratulations on purchasing a 270 with the big mill (496) in it. THAT is the correct engine, imo, for that boat. MT

Black_Diamond

You can get very high output alternators, but you may need to increase your wiring to handle the current and you may need modifications to the belt drive and more Amps means a bigger alternator too.