Interesting observations reguarding prop pitch
and RPM. Our boat is 55,000 disp with a 115 Westerbeke
6-cyl; 2:1 Twin Disk reduction gear
and a Hundested variable pitch
control to the 3-blade 24 inch prop. We run comfortably at 950 to 1200 engine
rpm and around 7 knots in flat seas & windless. 4 nm/gallon is about the rule
for us. I can run up to about 2500 rpm and vary the prop pitch which is useful for increasing the thrust at low boat speed such as in maneuvering or pulling off a surprise sand bar. I can run at the higher rpm and reduced prop pitch at up to about 10 knots but higher total power demand for sustained periods results in overheating
. All heat exchangers were de-scaled this spring and the system is clean.