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Author Topic: Prop size  (Read 1294 times)


  • Full Mayhemer
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    • Driftaway Natural Arts and Crafts
Prop size
« on: October 04, 2012, 08:11:48 pm »

Hello, need some advice, I am building a 1/18 scale trawler from a hull i brought of ebay I have drawn a set of scale plans and intend using a 600 size motor with a viper marine 20 esc will a 40mm prop be ok or will it be to big for the esc to cope with??

Tug-Kenny RIP

  • Full Mayhemer
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Re: Prop size
« Reply #1 on: October 04, 2012, 08:36:19 pm »

To answer your query, I would suggest running your 18th scale boat on a bigger motor, like a 900 with at least a 60mm prop. The motor will run at a slower speed with a better pull factor, and the battery will last longer on the water.

I have done a survey on my Fairmile blog, which covers the 600 motor, and here is a quote.

I have been working today on wiring up my twin 600's in my Fairmile boat.

I wired in an amp meter before testing and was severely surprised with the current consumption. As I was still lining everything up for smoothest running I was able to watch the current loads under different circumstances and have some info which you may find interesting.

Initially one motor took over 16 amps  (on the bench, with no water to push around) at full throttle.  After re-greasing the prop shafts and getting them true, it dropped down to 11 amps on full speed.  (noisy it was as well). At half throttle things seemed much better and it ran at 4-5 amps.  If I run two, with 35 mm blades I should imagine I'm not going to get more than half an hour running on a 7 amp hour battery.   :o 

Hope all this helps.


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