I haven't had any experience with any brand of BLDC/PMAC motor besides Motenergy. I will say that they seem to be great motors, though. However, be aware, very aware, that like most similar motors, there is no integral thrust bearing, and they are absolutely not designed for any axial loading. IOW, you cannot simply couple the motor to a prop shaft with no thrust bearing installed on the shaft. As the prop turns it is pushing the shaft forward (or aft, in reverse!) and that push must not be into the motor or it will quickly self destruct quite spectacularly. The thrust bearing transfers the thrust of the shaft to the hull safely, assuming proper installation and alignment. A prefab reduction gear, whether belt or enclosed gearbox, will contain and function as a thrust bearing. Motenergy makes several motors in 5kw and in the10-12kw range that will run happily from the typical 48v e-boat bank. Most will also run at higher voltages and many that are rated at 72v or 96v have been used in 120-144v nominal systems with no ill effect. They are best ran at rated speed, when running at full power output so loading the motor heavily at low RPM is inadvisable as the internal cooling fan will not be able to do its job. So for these reasons, unless you know what you are doing, a reduction gear of some sort is usually advisable.
Some of the newer Motenergy motors use what is called a sine/cosine encoder instead of the hall sensor array that is more or has been more popular. You have to use the correct controller for these. Mine have all used the hall sensor, and I have ran them with three different Kelly controllers, two square wave and one sine wave. The sine wave controller runs these motors considerably more quietly. Kelly can be difficult to get technical help from due to the language barrier but I like how easy it is to customize the controller. Only a usb-serial converter is needed to interface with a computer. Unforttunately they refuse to port their software to Linux so if you use the superior operating system you are stuck with borrowing a computer to configure your controller. Some also can be configured from an android device, however. I have not tried this. I kept a WinDOHs laptop just for my controller for a while but space is an issue so I ended up tossing it. The other major player in BLDC/PMAC controllers is SevCon and I understand that they are not so simple for a user to configure. Also I may be mistaken but I think Golden makes (or rebrands!) controllers for their motors?
Motenergy motors are air cooled with internal fans. Golden has at least some motors with water cooling. If you will be exceeding current or voltage rating significantly, I would expect a liquid cooled motor to handle it much better.
Lynch motors are designed for direct drive applications. Not sure if they are currently still in production or not. They are more expensive.
Best bang for the buck is probably the Motenergy ME0201014201 which can handle 100a at 48v in sustained operation and can be had for around $400, sometimes less. If you are worried about a cheap motor not standing up to normal use, get a spare like I did. I will say though, I have never had occasion to even open the box that the spare motor shipped in. The 4201 is wound for slower operation than the similar size ME0907. That is neither a bad nor a good thing. It is just something to concern with when selecting the prop and reduction gear you will use. Note that spreadsheets and formulae don't always jive with real world facts. For instance when I went to a bigger prop I thought I should change from 2:1 ratio to a 3:1 gearbox, but my efficiency actually dropped. I tried direct drive with a thrust bearing but even though I was not able to align the system correctly I still saw an increase in system efficiency over the 2:1 gearbox. So be advised that the motor and reduction calculated to give best results may not actually do so, and some tinkering and experimenting are part and parcel of an optimized system.
Kelly phase terminals are labeled A, B, C, and Motenergy phase terminals are labeled W, X, Y. Hall sensor connections are a crap shoot. So if you hook up your motor and it doesn't work properly, you need to try different connections. It will not turn, or it will turn slowly and draw a lot of current, if there is a mismatch. Properly matched, the motor will whizz smoothly with no load attached so better have it bolted down when testing. The rotor inertia will send the case spinning in the opposite direction and it will er, surprise you. Kelly can usually help you get it right the first time since they will specifically configure the controller for a Motenergy motor.
These motors have a 7/8" shaft. So if you will be mating it with a gearbox having a 1" input coupling, or if you will be coupling the motor directly to another 1" shaft, you will need to use a 1/16" thick bushing to bring it up to 1" diameter, and you will need to modify a piece of keystock to fit the two different keyway slots.
The motor is usually mounted via the face of the motor through which the shaft protrudes. The face is compatible to the ANSI "C" face and so these motors are readily interchangable with the same size mount plate cutout and the same bolt hole pattern. The mounting bolts go through the mounting plate and into the motor face. I suspect that the Golden motors are also "C" face motors.
Brushed motors must not be used on a boat having gasoline or propane equipment or accessories onboard. You can guess why, I am sure. But if you will absolutely NOT have such devices onboard, then a brushed motor is worth considering. A pull from a salvaged forklift, maybe?
So, two thumbs up from me on the Motenergy brand BLDC/PMAC hall sensor type motors.
