There is no need for a broad power curve.
The only rpm the engine will operate at during wot is whatever matches the load of the pump.

At wot the engine will always run at one rpm...... no matter how fast or slow the boat is going.

At lower engine speeds, there’s less load....... so having lots of low speed tq does nothing for you.

It’s not like a car where going up a steep grade at 2500 requires more work than going down hill at 2500.

With the jet....... you’re always going up hill....... and it’s always the same “hill”(load) for any given rpm.

Using Marks specs, at 3000rpm the load from the jet equals 146hp/256ft lbs.
It doesn’t matter that you might have 371hp/650ft lbs on tap at that rpm.
You can’t provide any more load to the motor at that rpm than 146/256.
If you apply more throttle at 3000rpm than is required to make 146/256........ the motor just revs higher.
The only way to increase the load is to turn the pump faster.

You keep adding throttle, the rpm keeps going up.....until the motor doesn’t make enough power to gain any additional rpm.

How heavily the boat is loaded, and how fast or slow it’s going has no affect on the engine speed.
The motor will go right to full rpm as soon as you go to wot.