Help getting enough power to my motor.

[Littleredhonda]

So I currently have a 3800kv brushless motor with a 9v max and a max of 50000rpm. My esc has a max of 35 amps. I have one 5200mhz 2s lipo with 7.4v powering it but I'm having trouble getting enough voltage to my motor to get the boat up to speed. Since I have two of those lipos, I was wondering if I could run both together in series to get more voltage to the motor? The boat I'm using it in is a 28" New Bright Sea Ray that I am trying to repower with hobby grade parts. Any help or advice would be greatly appreciated!

[Bande1]

4s is probably too much. get some 3s batteries.


these are cheap and decent with 10awg wiring. large wiring is important with low voltage.
https://www.amazon.com/Nihewo-Batter...s%2C220&sr=8-5

[Peter A]

It is not a voltage problem that you have. Your esc is too small. This boat with a submerged drive and plastic prop will have very limited performance, it may not even plane, it is a toy grade boat and not designed for high speed running.

[NativePaul]

Unfortunaltly you have a mix of parts there that aren't really suited to eachother.

3800KV is in a bit of a dead zone, lower Kv than you would really want for 2s and yet higher than you would really want for 3s. Probably best suited for 2s, and the 9v max means it isn't rated for 3s (which is strange because 3s would be well under 50,000rpm and its normally the RPM that limits the voltage), and that makes me suspicious of the motor, what brand, mass and size is it?

A 35A ESC isn't enough to power a 28" planing boat.

2x 2s packs in series is 4s and what most people would power a 28" boat with, but neither the motor nor ESC will take 4s with a boat that size. (I'm assuming you mean 5200mAh when you say 5200mhz)

If the motor is big and good enough you could potentially upgrade the ESC to something 200A+ and run 2s with a prop about 45mm, but ideally you would upgrade both the motor to something around 2000-2200kv 3650-4070 size and run your 2x 2s packs in series as 4s with a 150A+ ESC and a prop about 45mm, this would have a much easier time pushing your boat and would be suitable for a future hull upgrade.


Edit; after typing that based on what you said, I googled new bright sea ray and found an 18" boat, if it is an 18" boat you have not the 28" you mentioned forget what I said above in red.

A 35A ESC is fine for an 18" boat as long as it has water cooling, the KV is still weirdly intermediate but will work alright on 2s with a prop about 35mm, I think the battery size is a BIG issue though (pun intended), 5200mAh is way too big and heavy for an 18" planing boat to carry, look for something around 2200-2500mAh <150g.

Also that hull doesn't look good hydrodynamically, I understand that it can be fun to turn a toy grade RC into a hobby grade, and I'm sure the progress you will make over stock will be impressive, but when you reach the limits of the hull if you find yourself stagnating, please don't think that is all the hobby can offer you and give up on it, when you get to that point consider upgrading to a hobby grade hull of a similar size like the Ecomaster Mini Slider or Tenshock Mini Scord which would be much more capable, and allow further progression.

[Littleredhonda]

Ok, thank you for the help! I am very new at this and am still learning a lot. New Bright actually made two models of the same boat. The 18'' was more for pools and the larger 28", which is what I have, is for ponds and lakes. I will search for a new 2000-2200kv motor and a series connector, unless you think a 3s would be more suited. The motor I currently have is a 28mm GoolRC. Here is the link to it:
https://www.amazon.com/dp/B09YM415MX...v_ov_lig_dp_it

[Bande1]

Ok, thank you for the help! I am very new at this and am still learning a lot. New Bright actually made two models of the same boat. The 18'' was more for pools and the larger 28", which is what I have, is for ponds and lakes. I will search for a new 2000-2200kv motor and a series connector, unless you think a 3s would be more suited. The motor I currently have is a 28mm GoolRC. Here is the link to it:
https://www.amazon.com/dp/B09YM415MX...v_ov_lig_dp_it

here's what I would get

motor - https://www.amazon.com/dp/B0BG2PZMHV...ing=UTF8&psc=1
esc - https://www.offshoreelectrics.com/pr...ose-R-150C-Ec5
battery - https://www.amazon.com/Socokin-Batte...719962&sr=8-23

[Littleredhonda]

Thank you for the resources!

[1coopgt]

I was going to suggest this esc https://www.offshoreelectrics.com/pr...?prod=ose-R-90

[Xrayted]

So I currently have a 3800kv brushless motor with a 9v max and a max of 50000rpm. My esc has a max of 35 amps. I have one 5200mhz 2s lipo with 7.4v powering it but I'm having trouble getting enough voltage to my motor to get the boat up to speed. Since I have two of those lipos, I was wondering if I could run both together in series to get more voltage to the motor? The boat I'm using it in is a 28" New Bright Sea Ray that I am trying to repower with hobby grade parts. Any help or advice would be greatly appreciated!

How slow is slow for your boat OP? I took a look at a few videos of your particular boat, and its a scale cabin cruiser design that is meant to move in a slow, scale fashion. That boat isnt going to come up onto plane and move quickly.

I have a similar hobby grade boat from Pro Boat which is their scale tug that I use as rescue boat if needed. It too only runs about 10mph wide open because its scale and supposed to move slow. It will run on a 3S lipo for nearly 45 minutes and pulls practically no current at all, so the motor & ESC is barely above ambient after running the entire time. These scale boats come with low current ESCs because they dont pull any current with the scale movement. They do NOT need 150A ESCs!

Are you sure you want to invest real money into a motor and unneeded big ESC for this toy grade boat? Its going to look weird moving fast in the water if you do manage to get a more powerful setup up and running, and that's a big "if" because there is a lot more to making one run faster that just the electronics.

You will have zero prop options because that is a toy grade model that doesnt have the standard size stuff on it to easily swap over to other parts. That little plastic toy prop will likely be awful with a more powerful motor and just cavitate with more RPM and not accomplish much else.

That hull may also run terribly if moving faster because its was never intended to do so, and so no thought at all went into the design beyond the slow scale movements. Its very top heavy unlike any fast electric boat which is sleek and flat against the water, so who knows what is going to happen to that hull at higher speeds? Your going to have to sink a lot of money into it just to see if was complete waste of time for any of this. IMO, if you are going to buy lipos, motor and ESC, then just get yourself a proper faster hobby grade ready to run model to begin with and just leave that one for what it is. A slow, scale toy boat that would be great for rescuing other proper fast RC boats

[Littleredhonda]

Well it currently only goes about 5-7mph. I know it's about scale speed but where's the fun in that. I actually had it up to 20mph more or less with the stock gearbox it had on it but I removed it because I just didn't trust it with that much speed. It was all plastic and didn't have any bearings or anything.

[Littleredhonda]

For the ESC, would I need to get a program card to make it work with the motor?

[NativePaul]

It may depend on the ESC, but generally no. You need a card for fine tuning, but every ESC I have uses has functioned on the default settings straight out of the box.