upping the alternator output...

[Franki]

Hi guys, <br /><br />my old 72 Johnson 100HP is in excellent shape so I want to keep it for a while... the one thing about it that annoys me is that the alternator is tiny.. it barely supplies enough charge to replace the power used by the hydro-electric gearcase... and I have alot of electrical stuff on this boat.. fish finder, radio, nav lights radio etc...<br /><br />I have a small solar panel on the cabin roof which trickle charges the battery in sunlight, but thats not alot of use at night...<br /><br />could I possibly get the alternator rewound to produce a higher current? was there ever an option for a hi output alternator for these things???<br /><br />any tips would be great...<br /><br />rgds<br /><br />frank

 

[DJ]

Re: upping the alternator output...

Franki,<br /><br />It is not going to happen. <br /><br />If it was possible, it would have been done. The V-4 crossflows retained the same amp. rating until they were discontinued. A run of 30+years!<br /><br />I've never seen an aftermarket boost.<br /><br />The best solution is more batteries (switched) and more external charging sources. Sorry.

 

[clanton]

Re: upping the alternator output...

You could use the three holes in the flywheel to mount a pulley to drive an auto style alternator. You would have to make brackets and enlarge the cover, should be good for 60 amps. I would use grade 8 bolts and loctite in the 3 bolts that held the pulley. A super welder and machine shop may be able to increase the size of the rope groove in the flywheel large enough for a small v belt. Regulate the amps down to about 40 amps to increase belt life. The later model auto alternators are smaller. Small one would only make a small bump on the side of the cowling.

 

[Franki]

Re: upping the alternator output...

Clanton, <br /><br />I considered that actually,. I have an old 40HP rude here that has the pully on the flywheel, I was thinking of bolting it to the flywheel on the 100 and then rigup an alternator... (the rude has a toothed belt, so it could probably be replaced by a cam belt from a small auto 4stroke.)<br />I initially considered a VW generator, as they are long and thin, but not much output there either and slower spinning to boot. maybe I can even use the geny bracket from the 40rude to fit one to the Johnny... (or possibly the starter motor bracket from my spare 100HP...)<br /><br />has anyone tried this??? also, how much power would an external alternator take away from the useable power of the outboard???<br /><br />was just hoping that a $150 rewire would do the same thing.. its definately possible in theory.. but probably not in practise from what I read here... in my opinion, 9amps does not make a charging system. <br /><br />rgds<br /><br />Franki

 

[clanton]

Re: upping the alternator output...

I dont know about your part of the world, but I would choose a Delco alternator single wire. You can find different regulators and custom set the cut in voltage. I have a friend that has a automotive alt/starter rebuild shop, will stop by and see how small and cut in rates of alternator he has.

 

[Beaux]

Re: upping the alternator output...

Frank-<br />click on this link and read this thread. It was a little while back and some of the guys talked about the pulley idea.<br />alternator output increase <br />If you read some of the other links that are given within the above posting I hyperlinked, some give interesting info on custom rewindings and a link that asks the same basic question you did in which Schematic gave a tip concerning a cogged/chain drive verses a belt system to lower the torque on the flywheel. Good luck

 

[SlowlySinking]

Re: upping the alternator output...

Franki-100ESL72, one other thing you need to know is the maximum safe rotational speed of the alternator you choose. You need to know the maximum RPM's of your engine and the engine to alternator pully ratio to determine how fast the alternator will spin. Over revving the alternator could cause it to self destruct. The boat engine power loss depends on the alternator's maximum amperage output, it's a catch 22 situation, bigger amp units will charge your battery faster but use more power while charging, smaller units do the opposite. The worst case APPROXIMATE power loss would be the circuit charging voltage (about 14.5 volts) times the maximum alternator amps which equals watts which equals horsepower (746 watts is 1 HP) then you have the alternator efficiency rating to consider (unknown but way less than 100%) then add the frictional power losses of the drive belt and alternator bearings, fan, and power needed to rotate the extra mass. Easiest way to figure horsepower needed is ask someone where alternators are rebuilt or don't worry about it, assuming your engine starts easy the battery will be quickly re-charged, so after that the only extra load is the engine ignition, boat accessories, and losses listed above.

 

[Franki]

Re: upping the alternator output...

Thanks guys, <br /><br />This is much appreciated... I will look into all the links and would love to hear what you turn up mr clanton...<br /><br />It would be cool if I could hook up a variable resister or something to be able to easily change the output of the alternator...<br /><br />But I can say that the pully on the old evinrude is alittle smaller then the crank pully on a car... so it would most likely have less rotational speed then it would on a car..<br /><br />Thats ok because the outboard spends alot more time at 4000+ rpm.. so I suspect it would have to be less...<br /><br />rgds<br /><br />Frank

 

[clanton]

Re: upping the alternator output...

I look at a shelf full of delco alternators that are about 7 1/2 inches dia and 7 1/2 inches long can make 100 amps and uses the belt with 5 grooves. The alternator has 1 wire to battery, 1 wire to switch to excite the field and ground wire or ground case to block. I think the hard part would be making the mounting bracket. The pulleys should not be problem. The cover would have to be enlarged, and you could tell everyone that it was a turbocharger. Im not sure about this, but you may be able to excite the alternator after you are up to speed.

 

[Franki]

Re: upping the alternator output...

Does anyone know the charging specs of a 40HP evinrude selectric 1963 ????<br /><br />I ask because I had the gen in that rewound a few years back and hardly used it after that..<br /><br />If it adds something substatial to the charging system, i could put the whole thing onto the 100 HP in one unit, (its an external gen shaped much like a VW genny, with external regulation.)<br /><br />If its output is more then say 6-9 amps, it might be worth the effort.. I suppose unless anyone knows offhand the easiest thing would probably be to try and get the 40 to fire up and hook up the digital multimeter..<br /><br />The reason for my thinking are as follows..<br /><br />1. the bracket on the 40 could be made to fit the 100, and the bracket already fits the 40's gen.. <br /><br />2. The 40's gen is only 7cm diameter, and 13cm long, so it would be alot easier to fit and may not require cover mods.<br /><br />3. gen has only about 10 hours use on it, probably less.<br /><br />4. Using the pullies and belt off the evinrude makes the spinning rpm questions moot as both outboards would spend the majority of their time in the same rpm ranges. (plus its a toothed belt setup.)<br />5. it would probably put less load on the 100HP to produce its current, since it was designed for an outboard and a smaller one at that.<br /><br />So I guess the only thing stopping me from trying it is not knowing if its worth the effort..<br />It might be though, because the selectric gearboxes draw alot of current which the gen would have had to replace.. so without the selectric to draw it off.. it might put out a decent bit of current..<br /><br />Anyone know how I could find out??<br /><br />rgds<br /><br />Frank<br /><br />PS.. if I do this, I will photo and document from one end to the other and put it online.. it might be handy to someone else, and really old evinrudes are a dime a dozen at outboard wreckers, so parts are cheap..

 

[Franki]

Re: upping the alternator output...

Hi guys, <br /><br />I just did some googling.. and found the following URL<br /><br /> http://chblock.com/xr650r/stator.html <br /><br />It details the process of rewinding the stator for a dirtbike. (XR650 in this case)<br /><br />The principles are the same for an outboard stator.. I might try this, because I have a spare stator for my 100HP anyway..<br /><br />I guess the first step is to pull the spare out and see if it has any spare poles like the XR650 unit, that can be wound to increase the output..<br /><br />What do you guys think????<br /><br />rgds<br /><br />Frank

 

[SlowlySinking]

Re: upping the alternator output...

Franki-100ESL72, interesting link about the rewind. Look at it this way, all you have to lose is your time and some wire, but you stand to gain a lot of education from the research. Check the stator for extra poles and let us know. Sounds like an interesting exercise in home brew design. Good luck.

 

[Franki]

Re: upping the alternator output...

After speaking to many people a couple of whom were engineers, I have decided to drop the idea of putting in a gen or alt, or rewinding the stator..<br /><br />The reason for this is simple, at most I could possibly get the output of the stator up to 12-14amps at high revs, but thats not enough change to warrant the time or cost involved.<br />The gen would require alot of mods and testing.. not worth the effort for the gain either.<br /><br />I have instead come up with a different solution.<br />I am going to build a small generator.. (its actually someone else on this lists idea.)<br /><br />A small 2 HP four stroke lawnmower engine, hooked up to the biggest Alternator i can find. (possibly two if I can work out how to hook them up in tandum)<br /><br />The reasons are simple, <br /><br />1. The gen would be very small and much simplier to make<br />2. I could make it much quieter then the 100HP by hooking up a short exhaust pipe and small muffler.. it would be almost silent.<br />3. It would be very fuel efficient, it wouln't need to be on very much anyway.. maybe 40 minutes a day, or whenever I have the nav lights, spotlights, decklights etc etc for any length of time.<br />4. Doesn't require power to start.. (thats a big plus).<br />5. Won't require mods to the motor, which is great from a reliability standpoint.<br />6. Allows me to totally seperate the power for the accessories from the motor wiring system. (one will switch the other via relays.)<br />7. Inverters, with the gen running, I could hook up my two inverters and run them at full power. (I plan to have about an 80 or more amp alternator on it, depending on the power required to spin it at speed.)<br />8. Should be pretty light, lawnmower motors are pretty light, and the alternator won't weigh much.<br /><br />What do you guys think? would this be a goer? someone else on the list suggested this as something they had done.. so thankyou whoever you were. <br /><br />rgds<br /><br />Frank

 

[SlowlySinking]

Re: upping the alternator output...

Franki-100ESL72, sounds pretty good, I would opt for one larger alternator instead of two, the pulley arrangement could be a nightmare unless you use a double v-groove pulley on the engine crankshaft. Remember, a 2 HP output motor can only provide 746 watts per HP times 2 HP or about 1500 watts, assuming a 30-40% electrical/mechanical efficiency loss (rough guess and it could be worst) you are looking at about 900-1000 watts maximum output divided by say 14+/- system volts while charging and you get roughly 70 amps out. Now, that will be with the 2HP running full tilt which won't be quiet or last long. The good news is the maximum will likely only occur when charging a badly discharged battery, so, it will likely do what you want. Give it a go and let us know. Good luck.

 

[jim dozier]

Re: upping the alternator output...

I'm inclined to go with DJohns original comment that additional batteries properly switched may be the better alternative. It is way more simple, and an extra heavy-duty deep-cycle marine battery is not going to weigh any more that a separate genset and its a lot quieter. I have done and continuing to do a lot of sailing on large yachts which include a lot of stuff like microwave ovens and VCR's as well as electronics and cabin lighting most of which is accomplished off of 2 batteries which only charge when the motors running (not sailing). If you start with 2 good batteries, one primarily for starting the OB and one for accessories your current charging rate, although low, would probably keep you charged for extended use. If you want to fish away for a weekend, get a third battery. Its not as cool as inventing a new charging system but in the end will probably work better. <br /><br />If you're dead set on a genset, Honda and Coleman make nice compact gensets. For the heavy in wallet, separate marine gensets for larger boats are available for more money.

 

[Paul Moir]

Re: upping the alternator output...

Here's a site you might want to look at. As for point 2), I understand that for side valve engines most the noise you hear is from the engine, not exaust. OHV engines usually benifit way more from a super muffler. Too bad you can't cowl a lawn mower engine... ~900w sounds a lot better than ~200w anyway.<br /><br />PS - I had a look at one of those flywheels again. I see what you mean now.

 

[Franki]

Re: upping the alternator output...

Hmmm... I am sorta excited by the prospect of this little genny...<br /><br />Its a cool project that would be handy in places other then the boat... <br /><br />i wonder if there are small 2.5 HP OHC lawn mower engines??<br /><br />I know I could probably scrap though with just extra batteries.. but I am sick of "scraping though" I want the whole hog..<br /><br />Also, batteries kept topped up last much longer then batteries that are charged/discharged regularly. (thats for lead acid batteries anyway.)<br /><br />There has to be a quiet 2.5HP moter somewhere, I just have to look...<br /><br />I'm kinda excited at the prospect.. Its much preferable because messing with my main outboard in this way made me nervous.. this is better.<br /><br />rgds<br /><br />Frank

 

[Franki]

Re: upping the alternator output...

Incidently, Paul<br /><br />Thanks for that link...<br /><br />Makes very interesting reading...<br /><br />I am going to do it...<br /><br />rgds<br /><br />Frank