3s or 4s in Mini Hydro keeping the same max rpm the same.

[martin]

Hi Eric, I dont race so runtimes & cell weights are not relevent at all just pure fun & getting Max speeds for given set ups, I only run for short periods to keep temps down on hot set ups. Regards Martin.

[eric_laermans]

In Europe, SAW is always pushing to the max, seeking the limits. On 4s I assume 250A ESCs come to use combined with high pitch props. But I don't do SAW myself, only oval-heatracing (is a little cheaper).

[Rich]

Martin, from the data I have collected on my Eagle tree on my mean machine I would say running the lower kv motor on 4s would be best. I had a 4074 2200kv on 5s2p with an x640 (yes i know its a 4s motor) and got 180amps @57mph. Now I have a 4082 1500kv on 5s2p with an M545 and getting 145 amps @ 53.6mph. I am willing to bet the M645 I have yet to try will break that 57mph with less amps. As you will know it stresses the esc a lot less with lower rpm/amps. I lowered the rpm by about 13k unloaded and lowered my amps and got close to the same speed. I would give it a shot, you have many choices with all the motors you have go for it and let us know the results!

[sundog]

Remember, this is a 17" boat. And you're looking to increase the size of the tub for more battery space? I think you'll have more success at top speeds with a 2 cell lipo and a 4400kv outrunner motor. It will save weight, which will be the limiter here. Use a 60A esc to contend with the slightly higher amp draw and see what that does before opening the tub. IMHO.

[martin]

Been down that route 4400kv on 2s then went 3800kv outrunner on 3s on 60amp esc, The 3800kv on 3s was substantially faster with an extra 10,000rpm unloaded. Ive moved on since that set up to a much more powerfull Leopard 28 inrunner series motors 4400kv on 3s & 3400kv on 4s & 120a esc. Martin.

[larryrose11]

martin, Which Leopard motor? Boat? Prop?
3400 KV on 4s is attractive, but I was concerned with it blowing up from the RPM's. How does your rig handel it,
Im looking for an upgrade to a customized Starship rigger I have.

[martin]

Boat is a modded JAE Mini Sprint, modded by building a deeper tub to get what i wont in. I have some Leopards to use ie 2845-4420kv on 3s, 2850-4430kv on 3s, 2860-3400kv on 4s & Het 1w-30 4400kv on 3s. My previous set up with the 3800kv outrunner on 3s used an Octura x435 detongued & back cut 10 degrees.

[martin]

Drive hardware i also custom make as i use a .048" wire drive with 3 ball bearings in the strut. Also keeping run times short & 120amp esc helps out.