Tim wrote:
Red wrote:
Lew Hodgett wrote:
"Red" wrote:
snip
Guys, I'm in a little confusion here. I've run an alternator shop for
the past 30 years, but rest assured, I don't claim to know everything.

if you look back into the 70's your higher level cars (Caddies and
Buicks etc) used a 100A 27si-100 Delco alternator with a rather small
single pulley in 3/8 belt configuration, and they didn't have a
problem eating belts. Lincoln's and Mercs Used a 100 A Motorcraft unit
but did had a slightly wider belt, and had no problem with shedding
rubber.

I can understand using a mis match pulley configuration like a 3/8"
belt on the alternator with a 3/8" pulley and a 1/2" pulley on the
drive source (crankshaft) yes, that will eat belts.

In the past few years we've been installing the cs130 105 a. delco
alternators on mid 70's cars also using a 3/8' belt and pully with no
significant problems.

Granted a 105a Delco will put out about 130 amps on a full load, but
like the 110 a alternators on the yanmars, they don't run a full load
consistently. Once the battery bank is recharged, the alternator
output drops significantly to only an amp pull from the accessories.
So the torque on the belt is dropped considerably.

Any alternator that has to run a full load full time will burn out. If
you are pulling a 110 amp load don't expect a 110 amp alternator to
last very long.

Now if a person is running a heavy unit like a Leece-Neville JB
series, or 30si Delco or some big Niehoff, then yes, I'd say a double
by 1/2" belts and pulley would be manditory. because even then, the
field rotors are so heavy you have a flywheel effect to take into
consideration as well.

But it would still be interesting to know what the OP's alternator
make and pulley configuration is. Then I'd try to help to the best of
my capacity.

BTW, for the past few years, on my 23' Marquis cuddie (228 hp. 350
chevy alpha 1 mercruiser), I'm running a 105a Cs-130 D alternator
(with updated rectifier) , with single 3/8" belt, two batteries. on an
isolator. engine battery is a standard automotive, and the accessory
battery is an 8-D "Cat" battery. I've run the 8-D battery almost dead
several times, and the alternator has charged well, and the belt has
had no significant signs of wear.

Tim,
This is very interesting......
I do boat electrics, that is what I do. www.yachtek.com
I also know a lot (certainly not all) of what you know about old
equipment and applications.

Until the last five years or so, I would have agreed with you
completely. But, I have had it proven to me that about 100amp is all
the 10mm belt that lives on the front of most of the little engines will
take and survive.

I have fit quite a number of cruising auxiliaries with big assed
alternators. Most will eat a belt any time they go over about 100amps.
Unfortunately, this mistake is usually at my expense. Sometimes I can
tune a regulator to limit the charge rate and sometimes I have to get
(or worse make) a new larger sheave to slow the machine down.

Even the 4 cylinder Perkins with a full 1/2 belt are in trouble there,
but less so than the Volvos and Yanmars with 2 and 3 cylinders. If we
look at the differences, there are more than a few, and let's not even
get into automotive.
The smaller belt does us no good at all - Agreed?
The situation is always worse with the lower cylinder count, I attribute
this to the short term variation in crankshaft speed (something a V-8
has almost none of).
Another BIG difference, is that for a cruising auxiliary, you have to
belt the alternator to charge at rated (or best) current at cruising rev
not the rated speed. [One owner routinely blew up the FEAD belt
maneuvering into a slip because he would go to rated then.]
There is squat for airflow in any sailboat engine space.
Sailboats always beat up the batteries more because they always burn
them down and then want to change them completely on the way in the
harbor.

By the by, I have a motorhome that I have used for a mobile shop for a
while, that has a 455 and an 80 amp alternator (the old GM with two
pivot feet instead of a long single). Any time I've run the house
battery down, the alternator squeals for the first couple of miles. A
double belt is a common retro fit in this vehicle even without the 140
amp alternator. I do NOT like changing the inside belt.

Matt Colie