Calories Burned Calculation For Rowing Machine

Hello again everybody! Day 2 here and I wanted some advice regarding rowing machines. I've got a piston resistance rowing machine that is quite hard i.e. Lots of resistance. But there is no way to tell calories on this machine because it's really old and has no display of any sort. I was wondering if I could use my heart rate monitor to get a rough estimate of the calories I burn working out on this machine.

Also, since I have 28% body fat and my weight is 230 lbs I need to know what number I have to plug in to get a gross calorie burned estimate in online calorie calculators. Do I use my lean muscle mass of ~165 lbs or do I use my full weight of 230 lbs. I was told that for walking I need to use my full weight as it's a mass over distance matter, but I need to know about calorie calculation for different activities like rowing, renegade rows, burpees and others. For these exercises, do I use my lean muscle mass or full bodyweight?

Thanks a lot!
Max.