Some general information:
(Source:
https://www.drivesmartbc.ca/rules-road/equipment/brakes-boat-trailers)
The first thing that you need to do is know the total weight involved for the boat (and everything in it) and boat trailer (and everything carried on it) when you are ready to tow it. There are three divisions, total weight of 1,400 kg or less, over 1,400 kg but less than or equal to 2,800 kg and over 2,800 kg.
If your trailer and load weigh 1,400 kg or less, it only requires brakes if that weight is 50% or more of the licensed weight of the tow vehicle:
Trailer brakes
5.02 (3) A trailer shall be equipped with brakes at each end of each axle, but brakes are not required
(b) on any axle of a trailer other than a towing dolly if the licensed vehicle weight of the trailer
(i) is 1 400 kg or less, and
(ii) is less than 50% of the licensed vehicle weight of the vehicle by which it is being towed,
The licensed weight is commonly called the curb weight or what the manufacturer says that the vehicle weighed when it was first built.
If your trailer weights more than 1,400 kg it must be equipped with brakes:
Brakes required on all wheels
6.06 (1) Every bus, truck, truck tractor and commercial trailer shall be equipped with a service brake on each wheel.
Don't let that word "commercial" confuse you. If your trailer weights more than 1,400 kg, it is a commercial trailer by definition regardless of what you might think.
"commercial trailer" means a trailer, or semitrailer, or house trailer, with a gross weight of more than 1 400 kg, but does not include a towed motor vehicle that weighs less than 2 000 kg and is less than 40% of the gross vehicle weight rating of a motor home towing it via a tow bar;
You must also have a breakaway braking device:
Breakaway and emergency braking
6.07 (1) The service brakes with which a commercial trailer is equipped shall be of such manufacture and design and so installed and maintained that they will be applied automatically upon the separation of the commercial trailer from the vehicle by which it is being towed, and so that after such automatic application they will remain fully applied for not less than 15 minutes.
Finally, if the trailer weights more than 2,800 kg it must be equipped with brakes in the same manner as the over 1,400 to 2,800 kg category and those brakes must be able to be operated separately from the tow vehicle brakes by the driver:
5.02 (4) Brakes with which a trailer is equipped shall
(c) where the licensed vehicle weight of the trailer exceeds 2 800 kg, be capable of being applied by the driver of the motor vehicle towing the trailer from his normal seated position.
This essentially means that a surge brake is not acceptable for loaded trailers whose weight is over 2,800 kg.