HI Chris,
I dont think that motor will give much in the way of performance, I have use the 700 bb turbo, 12v on direct drive, and the 8.4 and 7.2 (I think!) on a gearbox reduction belt drive to give longer run time and cooler motor.
You can easily over volt the graupner 700 bb turbos, the nominal voltage is usually quite high, I use two 9.6 packs

HI Peter,
I like the twin drive belt system very much at 2 or 2.5 reduction it will save a lot on the batteries with a longer running time, Iv'e been looking at DC motors to go with this
Grupner have the low E motors 400 7.2v 3.3amp use
they run at 17000 on a 2.5 reduction would give 6800 at the props, I have given up on Brushless motors they are to tricky to reverse and I need one motor to run the other way, so I'm thinking of a Electronize controller,
with a subC 5000mAp nim cell pack. I think this mite work.

Regards Chris.

HI Chris
The last motors I bought were Turnigy SK2830 - 750 from e-bayer kinglipo-2008 in the UK. I teamed this with a quick 45amp esc sourced from China. I have looked on the e-bay site and he doesn't appear to be offering this motor at present. He has some low rev offerings but at a larger size. Have a look anyway just so you get the general idea.
Larger motors usually equate to more power Ie more current so this may present a problem in a 34" boat.
Dave

the higher KV motors are not faster just higher reving, they are unable to run with a decent sized submerged prop they normally run surface piercing props that are only half in the water try and run a submerged prop and they just melt unless they are very very small I used two 1700kv in my minI fire boat and they ran 25mm props,I will get my boat down and tell you the size of the motors
I have.

Peter

HI David and Peter,
Thanks for your help with the Kv on the motors ,I think
my Boat would have been out of the Lake and into the flower beds if I had gone for the faster ones.
Thanks Chris. 😛

HI Chris
Peter is right, anything much over 1000kv will be too fast. You should be able to find some at 800Kv which will be ideal.
Brushless motors are expanding at such a fast rate that it is difficult to suggest a particular model number as the stocks move so fast. The 28 refers to the diameter and the next two numbers refer to the motor length. The Kv varies with the windings/sectors. Sorry if I misled with the earlier post.
Good hunting
Dave

they both seem far to high a KV you need under 1000 kv I think mine may be in the 800s kv Ill check I got them from Overlander Ill find out the corect one they where not that expensive.

peter

HI Peter,
I have seen the Hobby mate HB 2835 out runners for my two motors they come in 2000kv and 3800kv please have a think which RPM would be best,
Iv'e ordered my 34" Fire boat hull from Kingston's it should come next week .

Thanks Chris. 🚤

if you look at the pictures already posted you will see the bearings they are stainless steel and we used on another project and they lasted 2 years with a lot more power than I will be using and where only changed when we went from 4mm shaft to 5mm.
hear are a few pictures of a test boat I bult to test the drive arangment another kingston hull P28

peter

HI Peter,
Thanks for the photos of your new boat, I am very Impressed with your work and the very light design, I was thinking of belt drive with only one motor in the centre, with the pros shafts front bearings mounted in in a ally frame to take the strain, if I did go for two motors witch ones would you think could be best.
I was talking to one of the chaps in my club "Claro Marine modellers" in Harrogate North Yorks and he is building a twice full size of the 34" it's about 5 feet long monster Fire Boat ,
Thanks again, Chris.

and some more, these may give you some ideas I wanted to make it as light as posable if you want any pictures of any are let me know and I may have some

Peter

Hear is one I started some time ago but othere projects and health stopped progress, I hope to sail it very soon as some painting has started already.I am using belt drives in the pictures but may well be direct drive before the boat hits the water.

HI Peter,
I'm sorry I haven't got any photos at the moment, I'm ordering my Hull next week,

Regards Chris.

HI Dave,
Thanks very much for your help I think two 28's should go well and a lot lighter,

Regards Chris.

Have you got any pictures of your fire boat I am building one from the same hull twin shafts.

Peter

HI Chris
Welcome to the site. I have a 34" Aerokits fire tender and use a 28 size brushless motor with Lipo battery, 11.1v 30mm 3 blade brass prop, all up weight approx 4lb. Being a small boat (relatively) weight will be your major obstacle. My model really motors with just one motor so I guess you could use two small brushless. You will need two speed controllers. There are many set-up on this site and I sure others will guide you re brushed motors. I am attaching details of my fireboat in the hope that it may help
Good luck
Dave