Richard,
I'm not familiar with that 'Kyte' motor's current draw so can't say how long it would run on that battery. I can give you a very rough 'ball-park' way of estimating it though. It means you need to know the maximum current draws of the motor and prop set up. And the capacity of the battery used to power the thingy. That means that you'd have to measure the motor's current draw with an amp-meter, at full throttle. Not really that difficult, just different (if you happen to have the ampmeter, otherwise a real P.I.T.A. - lol).
Once you know the current draw at full power, divide the battery's capacity (Ah or mAh rating) by the current draw. That gives the run time in hours (or fractions of an hour). The actual run time is going to be slightly less than that figure due to resistance and friction in the drive set up. So, factoring in a 'fudge factor', something on the order of about 5 - 10% less than the 'paper' figures, will give you an average run time at max throttle. How accurate is that? Oh, about 1 or 2 decimal places (not saying which 'side' of the decimal point that ends up on - lol).
The only other way I know of is by finding someone who also has your model and drive set up and asking them about their run time.
- 'Doc
PS - The 'quick-n-dirty' way of extending run time is with a battery with a larger 'Ah'/'mAh' rating. The only problems with that is that sometimes batteries of that size will sink the boat, or just won't fit.