What mounting dimensions does your motor mount have, all the 700s I have seen have M4 screw holes on 29mm spacing but many also have M3 holes on 25mm spacing, Brushless motors of suitable power are much more standardised on the M3 25mm spacing, so you may have to redrill your mounts or use an adapter plate to swap over.
If you are after the same performance but with increased efficiency at planing speeds, a 3674 motor will replace it, and weighs about the same so wont effect your waterline. Do you know the KV of the particular 9.6V 700s you have? The Graupner 9.6V 700 BB turbo is 1354KV and the 9.6V 700 turbo is 1562KV, as you can see there is some variation and yours may be a bit higher or lower than those, but if you went with 1600KV using the same battery and prop you should get similar performance, maybe a slight upgrade but well within the motor's limits. If you want a lot more power those motors are good for about double a 700 will give, but we would need to know more about your props including the pitch to give you any sensible recommendation for KV but up to 25% would be within the motors capability.
Info on the props would be good, many scale boaters use soldered brass props that will throw blades dangerously if you put a lot of power through them, or plastic props that will flex a lot. I am not big into submerged drive boats, but if you want to put a lot more power into the boat you may want to consider upgrading to solid cast bronze , stainless or alloy props if you don't have them already.
How do you drive the boat? While brushless motors are a lot more efficient when operating under heavy loads they are actually much less efficient when at very light loads so if you spend a long time at low throttle patrolling at displacement speeds you may find that your runtime doesn't increase or may even go down. If you want a lot of extra performance it will almost certainly go down.
Do you have water cooling on your motors at the moment? Water cooling coils around the can, and a short length of copper tube soldered to each motor connector can suck quite a lot of heat out of a 700. If you dont have good cooling adding it to your existing motors would be an easy and cheap way to get the motor temp down and add a touch more runtime.
I am a big fan of not running ESCs near there amp ratings for reliability, I like to keep my peaks under the continuous rating of the ESC. I assume you want forwards and reverse? Not really my forte as a racer I only use forwards, and my scale boat is a slow brushed one, so I would just recommend you buy the biggest one you can find/afford. if you wanted forwards only I would go 120A so your peaks are bellow the continious rating for maximum reliability, but I don't even know if anyone makes one with reverse that high. For what it is worth the most you can pull from a can ferite 700 motor continuously with good cooling is about 40A, and in boats a good rule of thumb is that the peak amps are about double the top speed amps, so if you are running your motors hot you may be seeing up to 80A with your current setup if it is one of the better 700s.
Last edited by NativePaul; 11-23-2019 at 09:23 PM.
Paul Upton-Taylor, Greased Weasel Racing.
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