The way I look at it is this - when the throttle is advanced to a certain point and left there, the engine starts speeding up as does the boat. The boat keeps speeding up until the engine's output matches the force required to move the boat at that speed. As long as there is "extra" force available, the boat moves faster. And as the engine(and boat) go faster the engine is developing more horsepower. There's never any "letup" or backing off on the force the engine is putting out unless the throttle is pulled back - with a commensurate reduction in speed.
Ken
Mehhhhhh....not really. No one has really mentioned how a mechanical governor actually works. When you operate the "throttle", you are setting spring pressure. That spring pressure modulates fuel going into the engine. That spring pressure is also regulated by flyweights. The faster the engine "attempts" to turn(ie low load), the more the flyweights move outward and adjust spring pressure and therefore fuel flow. So like Ski said, if you are under load and pull it out of gear, the engine will "attempt" to rev...the flyweights move outward due to centrifugal force to maintain spring pressure...and therefore maintain RPM.
Now the opposite is true as well. As the engine "attempts" to bog down when loaded up, the flyweights draw inward(due to spring pressure) therefore maintaining RPM but increasing fuel flow and therefore EGT/pyro temps.
Kchace, you are setting spring pressure and therefore RPM. So the engine seeks RPM....not equilibrium as you are suggesting. If it always found equilibrium then overfueling(black smoke/overload) would never occur. In your example, the engine will seek the RPM related to the spring pressure that is set, and the boat will do whatever with the power delivered. It may find equilibrium. It may not. It will try to find that RPM and fuel will be metered to achieve that. If the load is too great, the governor will keep dumping fuel and you will have black smoke and high EGTs....and eventually engine damage.
My explanation likely has many errors in it. Diesel governors have always fascinated me so I have done some reading. I am learning but still have more to go. Believe it or not, diesel governors and aircraft prop governors are similar. Their overall goal is different(although it is about RPM control), but the mechanics are the same. Flyweights governing a fluid. Oil pressure in an airplane constant speed prop. And fuel flow in a diesel governor. But the "control ;ever" sets spring pressure. And flyweights keep that spring pressure constant....
So in your example....I have a planing boat. I push the power levers up to a certain position/RPM. I look at the tachs...and guess what, they are right where I set them. Let's say 2200. The boat is still getting up and out of the hole. The RPMs are 2200. The boat is still accelerating. And once it is up and on plane and the equilibrium you mention, is met, the RPMs are still at 2200...ish. A gasoline engine would be bogged down coming out of the hole with a set power level position. As the boat comes out of the hole, RPM will increase dramatically as the boat comes out and reaches equilibrium. IOW, RPM as set at the beginning of the power up will be very different than the RPMs reached once the boat planes out.
As it relates to constant speed gensets...they don't have "throttle" levers. The spring pressure is set. So it maintains RPM regardless of load. Fuel consumption will vary based on load. RPM WILL NOT!!!
Ski????
You're right. My scenario is based on gas engines. I totally spaced on the governor being in the picture which will do as you say and provide a varying amount of fuel and thus power.
