The water boxer engine cannot reliably drive a larger alternator due to the
drive belt set. Most belt drives are designed around the belt having a 180
degree wrap around the drive and driven pulleys. On the waterboxer the belt
only skims around the drive pulley limiting the amount of friction available
to drive the load. This is why belt tension is so important and from the
factory a special high tensile strength belt was used.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
David Beierl
Sent: Saturday, September 22, 2012 11:13 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Alternator continuous-duty rating?

At 07:41 PM 9/22/2012, Rocket J Squirrel wrote:
>I don't think the 90-amp rating is a continuous rating. It's probably
>peak rating, or one-hour rating or something, but not continuous. I'm

Just some context - with 90 amps at 13.6 volts, assuming 85% efficiency the
alternator will be sucking down about two horsepower from the belt and
dissipating about 225 watts as heat.

I don't know how much the water pump uses, but you're definitely pushing the
edges of what most marine folks recommend driving with one automotive vee
belt, especially the 3L size that we use.

There's a little calculator at
http://www.gizmology.net/pulleysbelts.htm for required tension and such.
Only set up for two-sheave systems, but it's something.

I took squint around www.gates.com for hp ratings and got nowhere useful.
Stopped short of asking an engineer, which they provide for on the site.

Yrs,
d