Proper Sizing for Octopus Pump

[Turtle Blues]

Need some help on choosing the right size Auto Helm Pump.

So my steering ram size 17.7ci /290 cc puts me at the high end of the AF1212 and starting range of the AF2012 piston pump.
Thinking the 14.5 second hard over calc for the 1212 does not leave much in reserve. The calc for the 2012 would put me at 8.7 seconds at full volume however the application chart says adjustable to 15 seconds which would be ideal.
Leaning toward the 2012 but want to make sure this is not oversizing.
Would like to hear from anyone that has done this. Thanks

 

[Turtle Blues]

Maybe an easier question to ask.
For a twin engine heavy trawler in the 40 to 45 foot range what size pump do you have?

 

[ksanders]

First lets think how the pump works, as that will help you decide, since either pump will do the job.

A Autopilot pump is simply a 12 volt pump that changes direction by reversing polarity of the power.

There is no variable power here. The pump is either off, or pumping.

If you go with a slower pump, you will simply get slower corrections. This can feel smoother but it can also be slow to react in situations where you would want quicker reactions, for example in a heavy quartering sea.

If you go with the faster pump you will get the faster reactions you would want in a heavy sea, but you will get faster reactions in a calm sea as well.

The good thing is that your autopilot computer will learn how your boat reacts to overcome the tendency to overshoot that a fast pump would provide.

On my boat with my steering ram I was near he upper end of the smaller pump and went that way. Like you I could have went with the higher capacity pump and would have been just fine as well.

 

[Comodave]

Have you contacted the manufacturer and get their recommendations. That is where I would start. They should be the experts...

 

[Turtle Blues]

Guys,
Thanks for the assist.
Yes, the reaction time is the critical factor. The 15 seconds that the manufacturers literature says to calculate for seems a little lethargic, but appears to be the standard.
Yes, have sent the question to Octopus through their website but no response to date. Probably should repeat.

 

[OldDan1943]

Can the steering reaction be adjusted within the autopilot control unit?

 

[Antares]

I installed an Octopus pump on our last sailboat. It was an adjustable model. I set the response time as suggested. That worked great for what we needed. It was not too difficult to reset if we found the response too slow or fast. I thought the Octopus pump was one of the best things we added to that boat.

 

[Turtle Blues]

Dan,
Yes,I am driving the pump with a Raymarine SPX 30 and ST70 Autopilot so the system has a learn program and 9 sensitivity settings for most functions.
Antares,
Thanks for the . seems that anyone who has one is happy with it so that's a definite plus.

 

[Turtle Blues]

Received factory confirmation to go with the larger pump this AM.
Will update with commissioning results.
Thanks to all