Nomad Willy
Guru
We talk about this frequently but this is becoming one of the better discussions on this issue IMO.
And we're not even off topic.
And we're not even off topic.
Some tips from a marine engineer who works with diesels every day.....
"The governor senses the load delivers the amount of fuel necessary to maintain the rpm at that load."
Unless his recreational trawler has been retrofitted with a torque sensitive governor (in which case this whole discussion is moot) his governor only senses and responds to rpm changes either side of the setpoint determined by the "throttle" lever.
"As the load increases the governor opens the rack to increase fuel ..."
No, as the rpm decreases below setpoint the governor increases fuel flow.
" ...the governor on boat in question is delivering full fuel at a much reduced rpm."
The only time the governor would deliver full fuel flow is when it can no longer increase rpm to the setpoint. At that time the governor should limit fuel as the internal delivery control reaches the "fuel stop." It would take a seriously "over propped" condition to have this occur at any rpm setting below maximum.
"It is always over fueling all the way through its rpm range and it's been that way as long as the props have been on it."
The only time the governor would "over fuel" is when the load on the engine exceeds that which the engine can produce at a given rpm. This can be determined by the engine power curve. The propeller can be grossly over pitched or oversized but until the torque required to turn it exceeds what the engine can produce at a given rpm it will not present an overload condition.
I could believe that over propping is the cause if both engines ran 100 or so RPM below the governed speed. But these engines are shy by 500 RPM with a clean bottom, fuel tanks half full, water and holding tanks nearly empty and a 10' inflatable topsides. Carver engineers would not be dumb enough to OK that situation no matter what their marketing group wanted. Engine speed and fueling is controlled by ECM's and one is quite new. During sea trials the Volvo mechanic ran a heat gun all over the exhaust ,coolers, heads etc and found nothing alarming. It's a nice boat but I'n not going to buy it.
RC
I may be misreading what you said, but I'm not sure there is a direct correlation between RPM and fuel delivery. Even with a perfectly propped vessel. RPM and fuel consumption will independently vary dependent upon boat load, sea state and wind velocity.