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Old 12-12-2015, 02:04   #1
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Join Date: May 2011
Location: Mandurah, Western Australia
Boat: Roberts 57 Staysail Schooner
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Autopilot hydraulic pump - Should I oversize?

Hi all,

I am selecting the components for my autopilot and am most likely going to go with a Raymarine Evolution system. The boat in question is a 57ft full keeler displacing 30,000kg and is steered using 2 Hy-Drive 313 linked in series.

According to the Raymarine site, I only require a little type 1 pump for this setup. They clearly say that displacement does not factor in and only the ram cylinder size matters.

It just seems strange to me that such a big boat can be steered with the same pump as you would find on a 30ft light displacement production boat with a fin keel.

Should I go a size to a type 2 to be safe or am I overthinking this?

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Old 12-12-2015, 08:54   #2
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Boat: Custom Freya 20m
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Re: Autopilot hydraulic pump - Should I oversize?

Is probably more about what you have not mentioned - rudder size, degree of balance about the rudder shaft, and of course ram size.

I have a 60' modified long keel with fully unbalanced rudder hung off the aft keel and I need a substantially bigger pump.

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Old 12-12-2015, 09:05   #3
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Location: Lago de Izabal, Guatemala
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Re: Autopilot hydraulic pump - Should I oversize?

Seems like Raymarine has done the calculations for hyd flow and pressure and say you should be good with the small pump. I've worked on equipment that has 3 cylinders and the pump is no bigger than an apple. My question would be about the response time with the small pump and the big cylinder. Does it need to be slower or faster for a big boat like yours?
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autopilot, size

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