sorry, not to mislead anyone, it was a graupner 9.6v neo motor that melted the seasprint esc, and cut out the upgraded electronise esc, not the 12v bb turbo, bit of a typo error there!
This was prior to the gearbox, which has drastically reduced the amp draw. The point I was making was that you need to be careful with the amp draw of the motors, and make sure there is sufficient tolerance with the rating on the esc. I learnt the hard way! and as Peter has stated the electronise esc' s are repairable, otherwise that would have been nearly A£40 and it wasnt mine!, the ripmax seasprint isnt!
Hope that helps

If you intend running 2 700 motors, be careful with the esc, personally I think 40 amp is cutting it a bit fine, depending on the motor. if you google graupner motors, there is a link to amp draw, very useful, or look at my power set up, the link shows results of extensive testing, and depending on the motor/esc/prop/battery combo, the amp draw on some of the 700 motors is higher than 40amps. I fried an upgraded electronise 35amp with a 700 12v bb turbo, completely melted a ripmax seasprint, currently using a jetI 60amp, but this does not have reverse, as most of the high amp esc's are for racing and have no reverse.
However, now with a 2:1 gearbox, we suspect the amp draw is considerably lower, testing was planned for last wednesday, but weather was too windy!
Unfortunately, there is no defined formula, its down to testing, to achieve what you want,I am doing over 15mph, accurately measured, and its way too fast, bordering on unstable, but its great fun!!

the mixer is a unit which useually slows one motor down while the other stays the original speed sometimes works from the
rudder servo on a y lead when working properly you can turn the boat nearly rudderless hope this helps

Picture of Prop

the gear box can be made as I do or bought from MFA http://www.mfacomodrills.com/gearboxes/960d_series.html , these are a nice heavey duty unit.
the speed controlers I menthiod are from http://www.electronize.co.uk/fr30_series.htm I like them because they can be repaired cheapley, bit of a land rover of speed controlers all the parts that go are srandard maplins type items.
the batteries I would use would be 4300ah min you get a 1/4 more run time for the same size and weight over the older 3000 and they are only a little dearer.
props I use Prop Shop , not the cheapest but recently we tried about 10 props and nothing came close to prop shop props, we found the cleaver type of prop the best and have just orderd a few larger ones to try we where using 3 bladed 43mm but are trying a bit larger and a 4 blader as there was so much left in the motor and no heat
but it is down to experement. http://www.swangroup.co.uk/
the mixer is a unit that you plug both speed controlers in and the rudder it then has two outputs to reciver ane rudder one speed ctr it mixes the two signals so will alow you to just push the rudder to the left or right while stationry and it will run one motor forwar and one in reverse so it piroets in its own lenth, good if you are doing steering competisons , you can of course just use a Y lead. I hope this helps

Peter

taking what peter said,

the power set up would be

2x graupner 700's.
2x Mtroniks 40 amp ESC's
2x 9.6V 3000 + mah battery packs. (one for each ESC)
2x 40 or 45mm propellors.
1x standard 2 channell reciever + controller.
1x standard servo for the rudder.

I prefer mtroniks speed controlers to electronize but its up to you and for
a mixer I'm not sure what it is or what is does, but sounds useful.

here are the links,

ESC
http://www.westbourne-models.com/erol.html#1728x0&&http%3A%252F%252Fwww.google.co.uk%252Fsearch%3Fq%3Delectronize+esc%26ie%3Dutf-8%26oe%3Dutf-8%26aq%3Dt%26rls%3Dorg.mozilla%3Aen-US%3Aofficial%26client%3Dfirefox-a

Graupner 700
http://www.howesmodels.co.uk/RadioControl/viewProduct.php?ProdID=2732

the props, and radio can be found on

http://www.howesmodels.co.uk/RadioControl/viewProducts.php

batteries
http://www.rcplanet.com/Integy_Intellect_8_Cell_9_6V_3600mAh_p/int36008.htm

i'm not sure where you could get the gearboxes from but peter might know.

Have a look at this vid [url=http://modelfireboats.com/?v=23]http://modelfireboats.com/?v=23[/url] it shows a 34" boat going well your 46" boat will prob need this type of set up X 2 .

you can buy the gear boxes already made by MFA and the motor is a graupner speed 700 bb at I think 8.6 volts you would be able to run a 9.6 or even a 12v version he gets prob 20/25 min flat out and it is very fast it also stays stone cold so it could go faster with a bigger prop but it would be to unstable. so with a gear box and a 9.6 or 12v motor X 2 it would have a very good turn of speed without the problem of overheating or burning out controllers a pair of electonize controllers would fit the bill, I run a 34" boat on twin screws and it looked good on the water and I used a mixer from hunters so you can get very good control without the need for any more than 2 channels and it will piroet in it's own length. its well worth the effort I am building two others now both twin screw.Look at blog for minI fire boat, and Ill soon be posting the 34" boat.

Thanks for the info. I must confess I was starting to get confused looking at many different sites. if you have any links they would be greatly appreciated. 😊

I can think of a few power setups you could use in it, it depends how much you want to spend and how fast you want to go?


my freind at the lake uses this setup in his 46" safety launch and its quite slow but runs for about 25 mins.

2x 550 motors.
2x 20 amp Mtroniks speed controlers
2x 45mm 3 blade brass props.
1x 7.2V 4500mah battery.


if you wanted to go faster but spend a lot more I would recomend

2x Graupner 600's
2x Mtroniks 40 amp speed controlers.
2x Plastic 40/45mm props.
2x 8.4V NIMH 3600mah

with this set up you would have to fit water cooling to the motors.

Hope this helps, if you need web links just ask.

Help,

I'm pretty new to all this boat building business, but I've started to build one of Mike Cummings 46" fireboats. My problem is I wish to use two props like the real thing, rather than one, as the kit suggests, however I've no idea on what motors to use, voltage required or prop sizes.

Is there anyone out there that can help? 🚤

Has anyone got any plans for a solent class life boat as I am rebuilding one which I have, or do you know where I can get any from?

Thanks.