Flip,
It sounds like you used your motors well if they each have 4000hrs on them.? The Volvo is MD 2030 is closer to a 20kW motor than a 10kW.? A single 10kW system would be working hard to push the boat at 5.5kts in calm seas.? You may want to consider re-powering with a 20kW system and consider adding a 48v alternator to the diesel.
?
Kts???????? Watts
2.2???????? 480
2.7???????? 960
3.5???????? 1920
4.0???????? 2880
4.4???????? 3840
4.7???????? 4800
5.0???????? 5760
5.2???????? 6720
5.5???????? 7680
5.7???????? 8160? This is about max continuous power from a 10kW system
5.9???????? 9120
6.3???????? 11040
6.8???????? 13920
7.1???????? 15840
7.3???????? 17760?
7.4???????? 18720? Did the Volvo likely pushed your boat at about 7.6kts at full power
8.0???????? 23520?
8.5???????? 28320
9.0???????? 32640
9.4???????? 37440
9.8???????? 42240
Traditional Estimated Hull speed????????? 8.47??????
Mike? Electric Yacht
Mike Gunning