HI Folks
Being a toy aeroplane flyer primarily and have a few motors laying around

I am going to use a 3530 outrunner 1100 kpv motor and Esc from Giantshark about a tenner for the motor and a 40amp esc a tenner , in my RAF crash tender and a 2200 3s if if is too quick I can always use a 2s pack I will use a computer fan to cool the esc and duct it to the motor

prior to running sea trials I will test it in the bath with a wattmeter just to make sure it is with in specifications

regards emma

Outrunner Brushless motors work best. Better to keep the revs per volt to nearer the 1000 mark. Use a scale brass 3 blade 35mm. You do not need racing props. Using a small brushless motor and LiPo the weight of a 34" Fireboat will be minimal so you can easily achieve planing. My 34" nearly takes off and needs the ESC output reduced via the transmitter. A racing prop will also put an unnecessary load on the motor which will use more current, possibly overheat and may cook the motor.
IC engines were big and heavy so much of their power was used in combating the weight. Brushless motors are light and powerful so are much more efficient.

HI Scorrier,

I am currently looking at the same issue as I recently bought a 34" tender from Ebay, old but never completed. I had thought about installing a spare Graupner 700bb brushed motor which I believe is a popular choice but then decided to go the brushless/LIPO route.

If you look at brushless motors, they fall basically into two types; inrunner and outrunner. inrunner looks like a conventional motor with a fixed case whereas the outrunner has a fixed endbell and the whole case rotates with the shaft. Sounds weird but works very well

If you look at the Hobbyking site , they list outrunners in sizes comparable to I.c. engines, so looking at what you might expect to use in the crash tender, you need to look in the .15-40 section , probably at something that gives about 2000 revs per volt and plan on running at 11.1 volts (LIPO cells for this voltage known as 3S) this gives about 22000 revs max which is fine for getting this hull on plane. Outrunners also have the benefit of being very torquey compared to inrunners so you can use a decent size prop. I have an outrunner that I have been considering using in the tender, but it is listed as being comparable to up to a .46 motor which might be a bit much. I am still researching what to go for so any views would be welcome

I also have a 46" Crash Tender originally built in the 70's by my late father and myself. Originally powered by a Taplin Twin 8cc diesel (which I still have in a box in pieces) and then an OS 50 glow, it is due for a bit of renovation and I think that this time it will end up electric power. Any suggestions as to motor welcome

Totally agree with Twinkle.
Nicads and NiMhs are quite suitable but they will add considerable more weight to your model. For smaller models this can be a disadvantage. However if you wish to contain costs this may be your chosen option.
I would reiterate the advice on using the correct speed controler and charger with LiPo's. They are very uncompromising regarding overcharging and too low a voltage on discharge. The chemistry in the batteries can become unstable in the event of misuse and the process can not be reversed.
ESC's suitable for use with LiPos have a voltage sensor that cuts the power once the minimum recommended voltage is reached.
Special LiPo chargers have a small additional connection to the LiPo (usually via a small white plug on the LiPo) this allows the voltage of each cell to be accurately measured and balanced to the other cells in the pack so that at full charge all cells are within spec.
If you look on YouTube there are some interesting videos of Lipos that have been mistreated 😀

HI Scorrier

It is possible to run a brushless motor from Nicads / nimh batteries
BUT I know There is always a but
why mix old and new technologies the nimh are an inferior power source but saying that has fewer "problems or shall we say opportunities than lipos , but they are heavier , and don't supply the hi current that the lipo will
but they are less fussy if subjected to abuse , also the esc must be a programable one that will sense the low voltage settings as they are different for nimh batteries . lipos are cheap enough and a good charger and lipos are sensibly priced on the giantshark website
hope this helps regards Twinkle

HI Dave,
Thanks for the advice. is it possible to run a brushless motor from a NiMh battery pack instead of LiPo's?

My motor is an RC Smart 3480 outrunner with an EZ Run 60A ESC. 11.1 LiPo 2000mA 3 blade 35 mm brass prop. No need for water cooling, ESC has small fan cooler attached. All up weight, boat battery motor ESC and fittings 1900gm.