Elias Aarnio wrote in news:4832788c$0$2661$9b536df3
@news.fv.fi:

Hi,

I am looking for a more efficient alternator for an old Yanmar 1GM
marine diesel. The original is 35 amp and I want to have something
between 50 and 60 amps. There is a bunch of webshops selling
replacements but they are all 35 or 40 amp alternators.

Does anyone happen to know a suitable replacement, a car alternator for
example? The best solution would be an alternator that also has the
sense-terminal for voltage control.


Hmm....60 amps x 14.2V = 852 watts divided by 746w/hp = 1.14hp plus a
little loss as heat. I guess it's doable on a 1GM if it isn't loaded up
very much. It might require a prop change to reduce the propulsion load
to power it without overloading the little 1GM.

I've gotten a recent education about alternators when a boating friend
bought a new alternator as he was passing through here. He bought a new
alternator, but soon cooked it by constantly running it at a constant
hard charging level LESS than its rated output.

It seems "car alternators" and "boat alternators" are NOT "POWER
Alternators", but are made to recharge starting batteries quickly before
they have time to overheat! They are NOT rated for 60 amps CONTINUOUS
DUTY. They will put out rated output but will overheat if you keep that
output for any length of time.

I can't help you in Finland, but here is an alternator website many high
power ham radio operators are buying 100% duty cycle alternators from:
http://www.alternatorparts.com/

Notice how these high duty cycle alternators are NOT cheap like regular
car alternators are.....relatively speaking, of course.

http://www.alternatorparts.com/GM%20...%20upgrade.htm
This picture in a vehicle clearly shows the differences. Notice how much
more COOLING FAN and how the dual rectifiers are huge with their big
heatsinks.

The marine models have flame arrestors on them to prevent fume ignition
in boats. There's a fine screen the air goes through, probably lowering
the airflow a bit at the expense of safety.