T&T: Cummins 5.9 High Output Alternator Large frame & belt routing

[Brian Shanafelt]

Greetings list,

Some time ago I posted about upgrading to a large frame alternator unit - in
my case a 200A Penntex.

The project included discovering the proper mount and belt length changeover.
Rob Acker of Cummins in Grand Rapids, MI, was extremely helpful as he had done
this very change for a number of customers.

The reason for posting today has to do with belt routing (I have pics).  On my
motor, the belt was routed from the crank directly to the alternator, then the
tensioner, then the water pump and back to the crank.  This is the routing
that the engine manual shows, so I assumed this to be correct.

The problem was that in this configuration, the belt only wrapped maybe 90
degrees around the alternator pulley, which became an issue when the
alternator wanted to put out anything over 120amps - squeals and dust were the
result.

By dumbing down the regulator - Balmar calls this belt management, I was able
to mitigate alot of the noise/dust by limiting the output to less than
120amps.

Al Thomason of the list had sent me some pics of his solution to the large
frame alternator question(his mount has the alternator mounted in front of the
motor and independentally driven by an additional pulley on the crank), in
sending the pic of this he shows a different belt wrap on the motor.  His
configuration goes this way: crank, then waterpump, then alternator, then
tensioner.  This is far superior in that the alternator pulley now has a full
180 degree wrap.

Eventually, I posed the problem/question to Rob at Cummins.  I sent him a pic
of my motor, and a pic of the other one side by side.  I asked which was
correct, as well as wondering which way the water pump would like to rotate.
His answer:

"Hi Brian,
The answer to both your questions is YES!!! I can't believe the engine is
cooling correctly with the pump running backward! Additionally, I have never
seen the tensioner mounted in that position, learn something new every day...
The belt needs to be wrapped identical to picture 2. I'd get this done ASAP.
"

The funny thing about all of this is I got the boat with 240 hours on the
motor and have operated without any problems inspite of the backward direction
water pump.

I probably would have continued to do so if not for the alternator upgrade.

Incidentally, after correcting this routing problem, I can now get 200Amps out
of the alternator without the noise.

Since I just installed a much larger house bank of AGM's I want to be able to
charge at as high a rate as I can.

Pics of the belt wrap available for those interested.

Brian Shanafelt
Isobel K
37' Custom Pilothouse
Seattle