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[jaffa.2009]

hi there i have a MFA torpedo 850 motor in one of my boat but i would like to change it to a brushless motor has anyone got any idea which one would work best

[nick_75au]

Hi Jaffa
For similar performance, something around 1000 Kv and rated around 150 watts, this will give a tiny motor in comparison to the 850, if you want to improve performance Higher Kv and watts.
 More details on the boat and propeller used and will be able to provide more info
Nick 

[jaffa.2009]

thanks nick_75au the boat is a wooden 49inch perkasa mtb the prop is a 3 blade 35 mm brass i would like to get it on the plane more the 850 is fine but just needs a little more if you know what i mean

[nick_75au]

Ahh Ok then, those Perkasa's are capable of good speed, there are 3 in our club, all brushed and vary from about 20 kph(single motor) to 30-35(twin,looks very quick on the water), all running Darke Horse (ACTion in the UK I believe may be a source  ) geared motors and 50 or 55 mm props. So Brushed is still feasible for this hull.

Brush-less in this boat I would  suggest something like this and put a prop on her that draws about 20-25 amps, so probably bigger than the 35 you have now. Make sure your batteries are up to the task of supplying the current

http://www.giantcod.co.uk/xyh3542-1100kv-brushless-outrunner-p-403782.html

Interesting thread here, I get mine from Hobby City
 
http://www.rcgroups.com/forums/showthread.php?t=1021088

Nick

[SteamboatPhil]

Yoy could try a MMB 900 brushed motor on 24 Volts, that would make it plane and you will get a good 1/2 hr run time.
Yhis should give you an idea of what it goes like.

[funtimefrankie]

Gte a copy of Novembers Marine Modelling International... theres an article on doing what you want... to a 37 inch GF one

[stallspeed]

thanks nick_75au the boat is a wooden 49inch perkasa mtb the prop is a 3 blade 35 mm brass i would like to get it on the plane more the 850 is fine but just needs a little more if you know what i mean

A long time since this post so it's doubtless somebody has told you by now that the prop was just too small.
There is ample power in the 850 on 12 volts but if you are drawing less than 13 amps then up the prop or remove the torque ring if there is one fitted.The 35mm 3-blade bras prop suits a higher kv/lower torque motor like a 700 bb turbo.