T&T: Bilge pump sizing

[Mark Andrew]

This must be a subject that has been covered here in the past:

I've got a 56' steel boat with 3 water-tight compartments

We're completely redoing the systems onboard.

We have a choice between a belt-driven pump (an accessory from Caterpillar)
that we could plumb to each compartment.  It has a clutch handle to activate
the pump, while the belt and sheave always turn. (flow rate spec: 95gpm
@1,800rpm with 30ft of head).

Another alternative is, say, and Attwood electrical pump with a float
switch.  They size up to 2000gph (or 33gpm).

Is there some rule of thumb that has evolved regarding bilge pump sizing?  I
imagine that if you had a hole, you'd want the largest pump available, but
is there any downside other than the initial cost to getting the largest
pump?

If I went with the belt-driven pump, would it make sense to have small
electrical float-switched pumps in each compartment for any small leak that
might occur?

Got no basis for the choice other than that bigger is better.

Thanks,
Mark Andrew
"Black River"
56' Steel, circa 1955
Holland, MI