installing an automotive 80-90 amp alt on my Universal 5416?

[hellosailor]

"Hellos, can you give me the dummies guide to installing an automotive 80-90 amp alt on my Universal 5416? (kubota based) I don't want to hi-jack this thread.
__________________
Denise, Bristol PA, Oday 30. On Tidal Delaware River, Anchor Yacht Club. "


Denise, I've started a new thread rather than hijack the other one.

To some extent, you can just bolt up anything and it will work. I suspect you want a slightly higher result than that. To do it right, a pencil and paper (and for me, eraser) and some research is needed. This gets a bit involved--but it ain't rocket science, and it honestly involves nothing harder than looking up some specs and doing some simple ratios a few times.

For an optimum setup, your alternator needs to spin fast enough to start up and charge at engine idle speed. That's "speed #1".

Then you want the alternator to be spinning fast enough to put out full charge at normal engine cruising speed, that's "speed #2".

And finally, you don't want to burn out the alternator by making it go too fast at "battle speed", i.e. when you're fighting heavy wind and waves with fullengine rpm. That's speed #3.

So the first thing you do is write downhow many engine rpms you will be turning at those three speeds under normal conditions. Then you look for the output curves for your intended alternator--which should be published by the maker and available online or in response to an email. Some makers, notably the Japanese ones, will refuse to supply that information saying it is proprietary to the auto maker. Most US makers provide it openly.

If you can't get that information, you're taking pot luck and literally, you may wind up charging twice as long (because you're only getting half power from the alternator) or you may burn it out every couple of years because it is running too fast and hot.

Where do you start looking for an alternator? If possible, look at the one supplied with your boat. If you can get something else that has the same physical form, the same number of mounting legs, the same dimension from the mounts to the pulley, then you have less fitting to do, and the mechanics of the swap are much simpler. Sometimes you can use a different form and only need to shim out the mounts, or move the pulley. Sometimes there's very little engine clearance, and a larger alternator just can't be fit, so look it over.

Once you've found a larger alternator that seems like it will fit, you look at the output curves for it. It may say "Maximum output, 100A @ 6,000RPM" and show that it puts out 20A@1800rpm, 50A@2500rpm, 80A@4000rpm, with a maximum sustainted speed of 11,000 rpm and maximum intermittent speed of 13,000rpm. And these are alternator shaft rpm, not engine rpm.

What you need to pick out of that, is that the "100A" alternator really doesn't wake up until 1800 rpm, doesn't put out fill power until 6,000 rpm, and burns out somewhere after 10,000rpm. So now you want to match those three alternator speeds, to your three engine speeds (idle, cruise, full). Odds are you can't match up all three, but you can pick a pulley size that gets you close on one or more of them.

How do you choose a pulley size? The pulley on the alternator, and the pulley on the engine (usually the flywheel up front) each have a different diameter, and these form a ratio. That ratio will set the ratio of the alternator speed versus the engine speed. Since the alternator pulley is usually much smaller than the engine flywheel, the alternator usually runs much faster than the engine rpm. There are usually a small range of different pulley sizes available for any given alternator, to match it up to different cars. On a boat, you may need to have a machine shop MAKE a pulley that matches the size you need, unless you can find something close enough. This can be a $100-200 expense.

And this is why you want the pencil with the eraser, because you need to look at how all three speeds match up, see what pulley size might work, go back and do it again until you get a compromise that gives you the closest match at all three speeds--for whatever alternator you can find.

Here's an online calculator page that explains pulley ratios and sizes:
Pulley and RPM Calculator | Engineering Formulas - Culver Armature and Motor
You put in RPM1, RPM2, Diameter1, check off diameter 2 and it will give you an answer. Basically, the speed of the two shafts will be the opposite of the ratio of the two pulley diameters. If you engine flywheel has a 20" diameter and your alternator has a [correction!]5" diameter, the alternator will turn at 4x the engine speed. The calculator is useful when the diameters are, say, 3-3/16" and 18-7/8" instead of nice round numbers.

And of course, your pulley has to match the flywheel and the original pulley belt, for V-belt profile or serpentine (ribbed) belt. Keep the existing pulley, the machine shop or alternator supplier only has to know "match this!" you don't need to know the terms for the different V-profiles and the like. (Yes, there are specific profiles, all "V"s are not the same.)

I'm sure I've either left something out or not clarified it and welcome input from everyone else. I can tell you from experience that although it may take a couple of days to chase down information--somewhere out there IS an alternator that will fit. Will provide the extra power. AND probably will cut your charging time in half, if you match up the speeds properly.

The Delco companies (AC Delco and Delco Remy) are very good at answering their phones and providing information. And if you've got room for a big alternator, the "large frame" Leece-Neville alternators have many fans and a great reputation. Speaking of fans (literally) an alternator from a car usually just has one fan and stays cool from air ramming through the hood. For a boat, you really want an alternator with TWO FANS, fan blades in front and behind, to keep it cool in the more constricted engine space.

And someone will point out, an automotive alternator technically shouldn't be used on a boat because it has no spark arrestor. For a diesel engine, and a recreational boat, that's normally not an issue, just be aware of it.

Too much information?

[Maine Sail]

Denise,

The Leece-Neville 8MR series is a direct fit replacement for the old Motorola alts. The 8MR2069TA is a 90 amp version that works very well and has a shaft size that is easy to find cast pulleys for. They can also be easily converted to external regulation at a point down the road if you want. They can be bought for under $200.00 brand new and come standard with an adjustable regulator....



Here 's some close up pics of the 8MR series:

Converting An Alternator to External Regulation

Balmar uses this same alternator as the model #81.

[deniseO30]

Thanks Hellos, and MS! I suggested this because others I'm sure would want to save money over the cost of those white and blue alternators that are so very pricey. Helping others like me that would like to, but hesitate from "playing" with things that are unfamiliar is also a great reason to learn about auto alts on marine diesels. Plus I love long drawn out threads? LOL

[dabnis]

Denise,

Not sure, but your insurance company might deny a fire related or
other claim because a "non- marine" alternator was installed. I know,
picky, picky for a diesel powered boat but maybe worth checking
out?

Dabnis

[deniseO30]

uh.. let's not start "another" insurance rant D. thanks for your concern just the same.

[deniseO30]

Hellos.. another thing you've touched on... tachometers.

[h20man]

Originally Posted by hellosailor

....


Here's an online calculator page that explains pulley ratios and sizes:

... .....


You put in RPM1, RPM2, Diameter1, check off diameter 2 and it will give you an answer. Basically, the speed of the two shafts will be the opposite of the ratio of the two pulley diameters. If you engine flywheel has a 20" diameter and your alternator has a 4" diameter, the alternator will turn at 4x the engine speed.

....

I suspect that there was a mistype here... and what you wanted to type was a 5... so to write again.
If you engine flywheel has a 20" diameter and your alternator has a 4" diameter, the alternator will turn at 5x the engine speed.

am I getting this? or making a fool of myself. Unfortunately the latter is a natural state...

[hellosailor]

Thanks, h20man. Corrected in the post. This is why I'm not allowed to practice mathematics across state borders. And why I use calculators, often twice.

Denise, when you say "tachometer"...without a working tach to know what engine speeds you'll be trying to match, it would be hard to pick the right pulley size. You'd have to get one of the handheld (contact or non-contact) tachs to measure the engire flywheel speed.

And then again...some alternators have a tachometer output, others don't. Some boat tachs are run from the alternator, while others use a dedicated "tachometer pickup" sensor that reads flywheel teeth as they go past. Either way, YES, you have to accomodate or match whatever your setup needs.

MS's mention that a LN will bolt right up, be ignition protected, and adjustably regulated to boot, makes them a very good place to start looking. If they fit, and you can match up the speeds, that would be a way to go.

[h20man]

Originally Posted by hellosailor

Thanks, h20man. Corrected in the post. This is why I'm not allowed to practice mathematics across state borders. And why I use calculators, often twice.

....

Ah, I see you corrected the pulley size not the x factor.. but that works as well.

Now, since your post is corrected, I guess it would be good to delete my previous post, as well as this one, to insure that I do not look like some hallucinating madman... ranting about errors that do not exist..

Thanks by the way, as now I am sure that I understand what you were saying...

[deniseO30]

many years ago I saw someone with a hand held Tach that he would just put the rubber ended shaft against the center of shafts on motor shafts.