Old Prather 46" Deep Vee electric conversion

[GeckoDragon]

Hi all, new here and have a question or two:
I've been noodling an electric conversion for my old gas powered Prather 46" deep vee for a while now, and I think I have the basics worked out but want feedback from people with actual electric boat experience. I'm currently looking at pairing a 780Kv Leopard 56110 with a Castle Hydra XLX2 esc, and running on 8s. Is this combination sufficient, and will it handle the loads? It's a heavy fiberglass deep vee hull. My other question is do I need a pump for the water cooling system?
Thanks!

[Bande1]

No you don't need a pump. RC boats are cooled through water pickups in the rudder.

[fweasel]

Your setup will be very mild and you'll be able to run similar gas sized props from your old setup. Water pumps in electric boats are really only needed in very extreme SAW setups that generate a lot of heat in a very short amount of time and need the cooling to continue while the boat sits idle between passes. You'll be fine with a properly sized rudder with a single or dual water pickup.

[Peter A]

That setup will handle it easily. Those older hulls don't always handle so well at higher speeds so a "mild" setup will work well. Bearing in mind the faster you go the less runtime you get.
Are you running a submerged or surface drive?

[GeckoDragon]

Thanks for the replies!. It's a surface drive, and I intend to use the old running gear so I won't have to worry about fabricating a new steering servo mount. Water pickup is actually a through-hull just forward of the transom. If I want it to be less "mild" should I up the voltage to 10s? The Castle ESC is only rated for 8s, so what do y'all recommend instead? (edit: or maybe I could up the motor Kv from 780 to 950?)
A few pics so y'all can see what I'm working with (please ignore the mess, I'm trying to fit the contents of a 3 bedroom house into a 1 bedroom apartment...)
20231117_162436.jpg20231117_162555.jpg20231117_162609.jpg20231117_162623.jpg

[Bande1]

DDM racing has G260 promod kits on sale right now for $120. I replaced my TP 5670 12s electric system with it and the gas engine is faster.

[GeckoDragon]

Neat, but this is an electric conversion. I've no interest in fitting a new combustion engine. Thanks for the suggestion though

[koen]

the only thing is change the prop shaft in a surface drive it's a lot easier on the motor and esc and you can use bigger props (but start small and take temps every 1 or 2 min)

[Peter A]

Ok so that is a subsurface drive.
Stick with 8s but start with smaller props. Is the prop shaft 3/16"or 1/4"? If it is 1/4"you will need to get a new flex with a 3/16"step down for smaller props. I would suggest starting in the 55-57 mm x 1.4 pitch range.
Run, test, check temps, and current. you have plenty of room for parallel 8s 2P, the weight will not be an issue.
Start mild and work up to where you have it running as you want it. You may want to swap out the subsurface drive for a new stinger, rudder, trim tabs etc later.

[GeckoDragon]

There's no way this is a subsurface drive. It's an aerated prop that kicked a 7ft tall roost with the gas engine, and was visibly prop riding above 75% throttle. This isn't something I bought used and am trying to figure out- I built it new back in high school. I definitely appreciate the prop suggestions, but if those are subsurface they aren't relevant.
On edit- do y'all only consider surface drives to be where the shaft exits through the transom? Because it could be me just misunderstanding the common nomenclature. But the current setup is with a surface-piercing aerated prop, which to me says "surface drive." If I'm wrong on that, I'd love some clarification.

[Peter A]

Yeah I think you night be confused. There is submerged drive, where the prop sits completely submerged under the keel, surface drive where the prop sits with the prop hub above the keel, and what you have, which is sub surface wher the prop hub sits below the keel but the blades pierce the surface. This is what gives you a rooster tail.
You can disregard the advice if you like, but I have built and run boats this size, so suit yourself. I was just trying to be helpful.

[GeckoDragon]

Thanks for clarifying! Guess I need to brush up on terminology. Peter A, your advice is definitely helpful and appreciated- if I came off as combative, that wasn't my intent and I apologize.

[srislash]

There's no way this is a subsurface drive. It's an aerated prop that kicked a 7ft tall roost with the gas engine, and was visibly prop riding above 75% throttle. This isn't something I bought used and am trying to figure out- I built it new back in high school. I definitely appreciate the prop suggestions, but if those are subsurface they aren't relevant.
On edit- do y'all only consider surface drives to be where the shaft exits through the transom? Because it could be me just misunderstanding the common nomenclature. But the current setup is with a surface-piercing aerated prop, which to me says "surface drive." If I'm wrong on that, I'd love some clarification.

So having tried one of these old setups myself converted to FE, what happened with mine was the boat would ride up on the prop getting basically the entire hull out of the water which made it rock side to side violently. With the power of brushless motors and spinning at a greater rpm we aim for the bottom 1/3 of the prop piercing the water.
How did it run on the gas motor? Smooth and strait or rocking back and forth(chinewalk). If it ran ok then match the battery voltage up to what the gas motor used to run. Likely 15k rpm. A smooth running boat has a better lifespan although running loose on the ragged edge is entertaining
Shawn

[Bande1]

its going to be an awesome 90-120 second run on batteries. wait an hour, run for another minute.

[Peter A]

its going to be an awesome 90-120 second run on batteries. wait an hour, run for another minute.

I had a 45" mono that I could get up to 8 min runtime from 6000mah, speed was low at around 55 kph though. At 90 kph it could do two heat races on the same batts. The faster you go the shorter the runtime. You can be sure that this boats original gas setup would have been lucky to crack much more than 40 mph. To achieve the same or even better speeds would give a reasonable runtime it set up well. On 8s 2P you may well get 5 mins or more at 50 mph.