Model Forum / Radio Controlled / Water Models / January 2009

Math says, if you get 4 minutes of run time from an 1800 mAh battery pack,
you should get 11 minutes from a 5000 mAh pack.  Generally speaking, that is
probably the best you can do, given today's equipment.  Even with water
cooling, heat buildup in the motor and ESC will tend to limit run times.

Try changing to a 4200 or 5000 mAh battery.  Choose Nimh batteries over
Nicad because they offer more power density and don't have the chemical
memory problems of Nicads.  As for Lipo batteries, personally, I don't use
them in my boats - they are much more costly, require an ESC that supports
them, and a balancing charger.  I only use Lipos in aircraft models, where
their lower weight and smaller size warrant the cost and complexity.

When you get the larger battery, try this test.  After a full run, check the
temperature of the ESC and motor.  If they are very warm (say 150 degrees F
or more), the extended run time may be risking equipment damage.  If they
are only warm to touch (say 100 to 110 degrees F),  the run time is probably
OK, but let them cool off between runs.

When I go to the lake with my SuperVee 27, I take along 4 sets of battery
packs.  This lets me have 4 runs without having to wait for batteries to
re-charge.  Even though I have modified the water cooling to flow more water
to the ESC and motor , I still have to wait 20 minutes between runs for them
to cool down.

As for increasing the boat's speed, the easiest thing is to change props to
one with a greater diameter and/or pitch.  You'll have to experiment.
Beyond that, you are looking at running with higher voltages going to a
larger motor with a higher Kv (RPM per volt) rating.

Good luck,
Randy