depending upon the type of motor cooling it can be a problem. Most brushless motors are out runners so the case rotates! in runners are usually for higher speed applications (or driving a gearbox). if you have an idea as to the size of IC engine the boat was intended to have then this list may be a help
.049 or .051 = 100 watts
0.10 = 200 watts
0.15 = 300 watts
0.25 = 500 watts
0.32 = 640 watts
0.40 = 800 watts
0.45 = 900 watts
0.51 = 1020 watts
0.61 = 1220 watts
0.75 = 1500 watts
0.91 = 1820 watts
Since Watts are Volts * Amps ( I know this is not accurate for a reactive load like an electric motor but its a rule of thumb)
This gives you a ball park next point is the KV ( revs per volt) of a motor. The higher the KV the smaller the prop. Finally buy a Watt meter they are not expensive and give you a chance to " fine tune" a setup.
https://www.ebay.co.uk/itm/FT08-RC-150A-Hight-Precision-Watt-Meter-and-Power-Analyzer-w-Backlight-LCD-U3F1/223101148808?epid=23023179441&hash=item33f1dd5e88:g:LYAAAOSwV3pba1JA:rk:11:pf:0
Car ESCs ( usually) have a reverse function while the airplane versions do not. They are generally cheaper than boat specific ESCs.
