T&T: Bilge pump sizing

[Mark Andrew]

The pump is hand clutched.  Caterpillar was unable to provide any more
information other than the flow rate, and that took a lot of research...

>From the drawings, it looks like a centrifugal pump, but I notice a plug on
the inlet...wondering if that is for priming.  Not sure if in an emergency
if I'd want to wait for priming.

The pump comes with a valve that goes in the bilge with a one-way flapper.
Maybe the idea is that the pump should stay flooded...water from the intake
all the way to the pump housing.  Not sure if the flapper will be sealed
enough to keep a regular full amount of water in the pipes....not sure if
that is a good idea anyway.

Mark

-----Original Message-----
From: Vance Nelson [mailto:vbnelson at gmail.com] 
Sent: Monday, March 10, 2008 1:06 PM
To: msandrew at chartermi.net
Subject: Re: Bilge pump sizing

If your motor driven pump is hand clutched, can it run without water?  I.e. 
dry?  Will it self prime?  The combo of electrical and engine driven sounds 
like a good investment as long as the motor driven will not self destruct if

dry.

Vance Nelson
Superior Dreams GB32-340
Houghton, MI 49931
KC8RGO
----- Original Message ----- 
From: "Mark Andrew" <msandrew at chartermi.net>
To: <trawlers-and-trawlering at lists.samurai.com>
Sent: Monday, March 10, 2008 12:08 PM
Subject: T&T: Bilge pump sizing


> 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
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