Need help, anyone with Alternator kit on a kohler EFI Avenger??

[number1cas]

Could anyone here provide me with the dimensions of the pulley on the alternator? I want to make one on my lathe but need the inner, outer and width dimensions, I can figure out the angle from the belt and the crank pulley. I want to use the original belt so I would like to keep the alt. pulley the same size as the factory one.

PS
I am using a diffrent alternator from a Mercury Optimax outboard, it is the same thing but is 60 amps, the brackets, belt, crank pulley and all metric hardware are only $140 versus the $500 for the Argo alt. kit. The Opti alternator has a pulley for a ribbed belt like on the new vehicles so I need to build a new one.

[LarryW]

If you know the rpm range of the alternator you are using I would just do the math on the pulley that is running it and go from there. Try to keep it in the rpm range it was stock.

[number1cas]

If you know the rpm range of the alternator you are using I would just do the math on the pulley that is running it and go from there. Try to keep it in the rpm range it was stock.

Thanks Larry but I'm not sure that alternators really have an rpm range (within reason) The outboard it is from tops out at 6200 RPM and my ARGO is around 3750? (I think) I was more concerned with being able to use the stock belt size. But now that you mention it maybe i need to research and see if I need to resize the pulley to spin the alt faster as it was from a 6200 RPM engine and now a 3750? Guess I need some more info on alternators........ DANG always a catch LOL!!

[LarryW]

Im sure it would work, just not maximum power output. I have heard of the self energizing GM alternators not working at slow speeds because the need the higher speed to leak a voltage to energize the alternator. I am assuming yours isnt self energizing though. Probably has a wire for on/off.

[number1cas]

Yeah it looks identical to the Argo unit, has regulator in the back of it and one small wire connector to 12 volt to energize when the ignition is on, says marine right on it too. Only diff I can see is the pulley style and that the manual for the Opti says it has a 60 amp charging system. I would be happier if it only ran at 40 amps though so it doesn't rob too much engine power. i am scouring the web to see how diffrent rpms affect an alternator. Anyone with the knowledge is welcome to fill me in......

[Zircon]

Hi,

I bought the alternator kit when I bought the tracks for my machine, but I haven't installed it yet. Working outdoors with the tracks was cold enough ... I have to rent a concrete saw and enlarge the concrete basement of my two story workshop/shed so I can get the Argo inside with the plow on next winter :-)... so I have to wait until it warms up a little before I attempt that little job with the alternator, space being as limited as it is there inside that engine compartment. Problem is, right now I'm nearly 700km away from home ... and the alternator kit.:-) I should be back later this week or early next though, so if you haven't got the dimensions you want by then, I'll send you everything you need.

[number1cas]

So, as Larry mentioned, it turns out that most alternators DO operate in an RPM "band" of sorts. I have found that most start output at around 1000 RPM and start to really put out at 3000 RPM or so. Full output is at 6-6500 on most, it is a linear curve. 3000 RPM gets you 1/2 or a bit more of the full rated output. I have also found that most common alternators are okay up to 12,000 RPM, they just top out at max output around 6500. I would like mine to spin around 2500-3000 at idle so that I have 30-40 amps. So since my ARGO idles at 1000 or so and tops out at 3750, I am thinking 2.5:1 would be a good starting point. That gives me aprox. 2500 RPM on the alt at idle and 9500 at WOT. From what I am reading the alt bearings should be fine for this.
I am also going to measure the pulleys on the original outboard to see what they were spinning it at, although the outboard is 6-6500 at WOT and they get driven at that RPM MUCH more than an Argo would, but it will be a good reference to help determine a final ratio and see what the top rpm of the alt was on it.
FYI I also read that every 23 amps requires around 1 horsepower.

[LarryW]

Nice stuff! Thanks for posting that.

I never knew 23amps=1hp!!! That is more good info!
With the 23 amps=1hp thing, just so not to scare anybody I thought I would add. Lets make this easy with numbers, 46 amp alternator, its not going to be using 2 hp all the time. Only on full draw.

[thebuggyman1]

23 amps isn't 1 hp.......It's a little more complicated than that. 1 hp = 746 watts by definition, thats about 62 amps at 12 volts. The 23a figure must be due to the mechanical losses and other inefficiencies from converting one type of energy into another.

[number1cas]

Yeah, keep in mind everyone that anything I mentioned was based on everything I read, then filtered out what I felt was correct and then averaging that info. So it may not be correct, I have never given an alternator such in depth thought !! Oh well, I do love learning new things so this is turning out to be a great project. Maybe I will do the actual math and see what I can come up with, either way it doesn't seem to be very much horsepower and I doubt I will even feel the diffrence.
Feel free to put in your 2 cents or expertise, that's what makes this site so good.

Many, many thanks to Zircon for these pics




Cas

[number1cas]

Finally finished the alternator install. Had a wicked time trying to buy a 2.5" pulley for a 3/8" belt, everything I could find was 1/2". So i went looking for a chunk of steel that I could machine into one, but luckily a good friend had a selection of old alternator pulleys from heavy trucks, 2 and 3 belt pulleys AND 3/8" belts !!! Man I love guys who save everything!! One of the pulleys fit perfectly, a couple test fits, 2 or 3 spacers on the lathe and a bit of machining and grinding on the alternator itself and bam! she's done, and so far it is working perfectly. Thanks to all who helped. It was worth all the effort as the new alt has tons of power to run everything I have and then some, even the winch is improved. The no load speed is much faster and the pull is much greater now that it has 3 or more times the power.

[Zircon]

No pictures to show off all the work you did? :-)