Red wrote:
Lew Hodgett wrote:
"Red" wrote:

I was looking at a 3 cylinder yanmar a few weeks ago and found the
alternator belt was slowly being eaten. Since then I inspected 3

more

similar fairly new (all from new to less than 3 years old) racing
sailboats with the same engine and all were slowly eating belts.

Belt

tension was within normal limits on each. All of these engines had 110

amp alternators on a single belt pully.


Seems quite normal to me.

If you look at the Amp v RPM for that alternator, probably needs a
dual belt drive.

Lew

Yeah Lew, that was my point in replying to the OP. There was obvious
accelerated wear on each belt on each identical installation from the
factory. So I am in agreement about using more belts on high amp
alternators. I've been noting though that some people/technicians/boat
mechanics think that a 110 amp alternator is not high amp, but the
consistant belt wear proves them wrong. Of course, there is a possible
alternate explanation for this particular type boat - Balmar has
supplied some OEM's, in this case Yanmar on some of their engines, with
mismatched belts/pullies. SAE belts will be eaten up if run on pullies
designed to be shipped to Europe. As I understand it, the pullies
supplied have a different angle than the angle the supplied belt is cut.

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 lever 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 pully configuration like a 3/8"
belt on the alternator with a 3/8" pulley and a 1/2" pully 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
consistantly. 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 droped 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 pully 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 fo wear.