INA219 high current measurements for my autonomous boat?
You are two for two:

Yes, that is the sense or shunt resistor they are talking about replacing.

Yes, it is a 0.1 ohm resistor.  In resistor code, the letter describes the range and its location is the decimal point.  For example, 2K7 is a 2.7K resistor.  R for ones, K for thousands, M for millions.  There is no letter for the 0.001 to 0.999 ohm range, so the R is used with more zeros.  There usually is not a leading 0.  Thus, a 0.01 ohm resistor is R01 or R010.


For any given current, both the voltage across it (Ohm's Law) and the power dissipation (Joule's Law) are directly proportional to the resistance value.  You really want to stay with the same size for maximum power dissipation capability.  Here is a chart: