Hi GregHiltz, thanks for sharing your method. I read your procedure with great interest.
At least you have a working method and you're not just talking nonsense, like someone who boasts of his experience but has little real substance and a knowledge base that's too limited to boast every chance he gets.
I understand you're in favor of using fuses and you've given excellent advice on choosing their size.
I also (after studying the factory data) perform tests directly on the model and take measurements in various conditions (both dry and wet) as I mentioned in the previous message (in fact, I wasn't just talking about theory, but always performing targeted tests).

Hi BlackShoe, I also really appreciate your approach and the measurements you take. Thank you for sharing it.
You're right, many engines don't have data for various reasons.
I have many whose specifications I don't know, but some of my technical knowledge and targeted testing help me conduct targeted checks.
I also made videos of the electrical measurement tests I've performed on ship models.

P.S. Anyone who thinks everyone just copies from the internet is doing it themselves and can't realize and accept that some people have real technical knowledge. Envy is a nasty beast.

Mr. Shoe, I agree with everything you said, right down to the paint. Advice from those who have real experience is valuable. Useless banter copied from the internet is just an annoying and has no real value.
Lew

Greg and Lew, I agree completely. The motors I use are mutts bought off the 'net with no pedigree, label, brand, or spec sheet, so manufacturer tech is non-existent. When I have a new build and after I've proven the watertightness, I put the boat in my small pond, put the bow against the edge and run the boat (single or twin screw) at full throttle with an ammeter hooked up in series with the motor(s) for an extended period of time. Monitoring the amp draw and feeling the motors for temperature occasionally I can garner enough information in real time without a lot of theory behind the build. (Theory is good, but someone telling you the stove is hot, is not the same as drawing close to it and discovering for yourself indeed, it's hot.)
Once I know the loaded amp value of the system, I simply install a breaker around double the running amp load and call it good. (I am an advocate of the "KISS" principle. I also don't use any artificially over priced marine bottom paint, but that's another subject.😊)

This is after all a hobby and as such should be enjoyed rather than getting bogged down with a myriad of principles and over-the-top confusing data unless of course that's the part of the hobby someone thrives on.

In my 50 years of gearing up and running R/C boats, I have always been cognitive of fusing my systems , as at sailings I have seen boats blow fuses out in the water, seen some burn up their motors, and others fry their ESCs.
If I am using a known motor with established Amperage draw , I won't test the motor operation for max draw, but will install a fuse slightly above the stall /max amperage. If it is a motor without specs , i will bench test with an Amperage Meter at free spin( no-load), then run the motor while pressing the shaft on the edge of my workbench (under working load), and I will then lock a Vise-Grip pliers onto the shaft and hold the motor against the workbench then hit the throttle/ connect the power briefly to get a maximum amperage draw for few seconds. With this info, I will size my fuse to be just under that max. Amp draw. This would represent the boat getting caught in the weeds or perhaps winding fishing twine around the Prop and causing a near-stall.
I would rather pop a fuse than ruin a good ESC or smoke my motor and possibly burn up my model.
Cheers

I don't worry about fuses. Only have one boat with fuses. Very frequently I have been running motorized RC boats for almost 20 years. (The last 10 includes RC tanks.) Only burnt out one ESC during that period. (BTW, one way to make smoke.) Also, I haven't seen fuses in RTR boats as well.

Lew

Hi Black Shoe

Correct fuse selection is a topic that's been discussed several times in this forum, and I wanted to hear others' opinions (because, in addition to the theory, which is mandatory to know well, I value my own and others' experiences).
I'll answer you right away, but keep in mind the opinions of other modelers.

I should point out that I only placed the fuse between the ESC and the brushed motor, although, in my opinion, it's also appropriate to place a fuse between the battery and the ESC.
So, I'll start with this first: the fuse between the ESC and the motor.
You need to consider the factory specifications of the electric motor (and if you do some current measurements yourself under different conditions, that's even better).
For the brushed electric motor, the manufacturer specifies three currents:
No-load output current;
Output current at maximum efficiency;
Output current at lock;
You know that if you brake the rotating pinion, the electric current increases to its maximum value until it completely stops.
I personally choose a fuse size between the "Output current at maximum efficiency" value and the "Output current at lock" value, but much closer to the former. I used to opt for one and a half times the "Output current at maximum efficiency" value, but now I've gone for double, but I'm not so sure (because I like to be conservative).
For example, for a motor with a 12-amp "Output current at maximum efficiency," I choose 25 amps, but some might prefer a lower value, while others might prefer a higher value, as long as it's much lower than the "Output current at lock."
I'm very curious to know the selection criteria and values ​​used by other modelers.
The fuse must not blow when the inrush current exceeds its rating, so instantaneous fuses should be avoided. Before taking it out on a lake, I always do extensive testing in the bathtub, which I recommend to everyone.
Regarding the fuse between the battery and the ESC, I base my calculations on this criterion (based on reasoning supplemented by the opinions of several experienced modelers).
The fuse size should be a few amps (some say at least 5 amps) below the maximum threshold.
By maximum threshold, I mean the maximum current that can flow continuously, not the maximum peak current.
I only consider forward gear, but if you want to be more conservative, consider the values ​​for reverse gear, which are typically lower.
Some modelers, adopting a less conservative approach, prefer to slightly exceed the maximum current that can flow permanently to avoid premature failure. In practice, slightly above rather than slightly below this threshold.
The important thing is not to consider the maximum peak current as a parameter.

There's also the issue of wiring.
The wiring should be suitable for the currents declared by the manufacturer. The fuse could also protect the wiring. Another weak point is the connections between connectors, but I don't want to delve too deeply into that for now.
Capacitors between the terminals of the electric motor are also useful for other reasons, but that's another discussion and for different reasons.

This article on permanent magnet brushed electric motors may also be useful to you.

wiki/147457

no one has ever mentioned a fuse size before at my local club seems fuses are a black word I must admit only one of my boat has Any all this tech arguments cause great confusion we haven't got on the subject of two speed controllers rather than one that was my alternative the motors in my case are 550w brushed

Thank you.

Having revisited the thread I either missed it, or neither the proper gauge wire or the fuse value was mentioned for these potential amp loads.

Hi Black Shoe, I'm writing the reply, but it's taking time to translate.
In the meantime, I can tell you this: you don't need to apologize; I personally don't think you're being controversial at all.
Forum discussions are interesting and lively when there are differing ideas and opinions. The important thing is that it remains fair and courteous, without offense or unnecessary petulance.

Victor and Alessandro, sorry, I wasn't trying to be controversial, I was just sharing a couple of methods that work for me. I understand what the ramifications are of a stalled/disabled RC boat and what the potential results are.
My boats are slow, not very sophisticated, and pretty basic. SLA batteries, and brushed motors in every one with the exception of one that uses a LiFePO4 12.8V, but still brushed motors.
One point of confusion on my part.....with the high amp potential of the systems you advocate, what value fuse do you install?