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From: Dave Cooper (no email)
Date: Thu Feb 07 2008 - 07:28:51 EST
<Mark wrote in part: 24 volt starter...What do you think?>
Be happy :-)
A 24 volt starter will spin your Cat faster, draw 1/2 the current of a 12
volt so the wiring resistance has less effect and the engine disconnect
switch will last longer. What's not to like?
A 12 volt starter on this engine will have stall amperage of over 2000 amps,
if I recall. That's more than most disconnect switches and 4/0 gauge wiring,
terminals are rated for. The 24 volt starter will be half and within the
limits of all the normal heavy duty switches and a nominal run of 4/0 wire.
Find a pair of high quality group 31 start batteries that have a CCA of 1200
ea or more. Series them up for 24 volts and then put in a small ~20 amp
dedicated smart charger or at least one that cuts off after a charge cycle
and back on if the voltage drops under a preset limit.
Connect this to a suitable dedicated small sine wave inverter that can
handle the peak load of the charger and connect it off the house bank.
Voila an independent starting system that will outlast you.
If the charger or sine wave inverter were to go TU for any reason you can
always charge the start batteries one at a time from any 12 volt source.
However, the G-31's should be good for 10 starts or more without charging so
as long as you have a meter to check the battery voltage you should never
find yourself unable to start. A good check of the capacity is to try it at
the dock. Start the boat every day until it won't start. You'll be amazed at
how much power there is in a pair of good G31 start batteries and how little
of it is used during each start cycle.
We have a 24 starter and it's peak on our 6-71 is 620 amps and start to
finish the cycle is 2-4 secs or often less. This is a lot of current little
time so very little battery drain. I would expect you the Cat to run a bit
longer cycle of perhaps 3-6 sec's and your normal peak to range from 800 to
1200 amps at temps down to 45 degrees or so. Again not a lot of battery
drain.
Make sure you run 12 volt power for your gauges/senders/alarms and not 24
volt! These are often picked up from the key switch terminal but as you had
an air starter then more than likely the 12 volts is supplied independently
from the old start circuit. Also the 24 volt starter is most likely to be a
isolated unit so the negative of the battery needs to be tied into your
ground system at the common ground point.
I'm somewhat surprised that your mechanic would change for an air start to
an electric without being able to check out the system...i.e. starting and
running the engine normally. They should at least explain then need for
changing over the items that you have as every installation is different as
are our boats!
Good luck...be as happy with the 24 volt starter as your Cat is :-)
As always YMMV...
Dave & Nancy
Swan Song
Roughwater 58
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