Thats a heckuva big lump of lead to stick inside the hull of a yacht. A 5 pack of "C" size NiMH will do the job just as well, but still leave the yacht able to perform as a yacht. Packs available pre built.
A 385 motor (same size as a 380, more poles, not as thirsty) will give the required power. Use it with a 2 blade prop about 30mm diameter. Less blades, less drag. Same with less diameter. Control it with a Mtronics Marine Viper 10. Krick's "standard" motor might be anything, measuring the can is a start, but doesn't tell you what is inside.
Any motor with "38" starting its number will be 38mm long, as will any "400" series motor. Some manufacturers rounded up the number to make life simpler for some.