Sounds like what you need is a strain gauge to measure the loading on the drive. Reach out to Mike Clesceri (MDC DriveGuardian) he can help you.

An auto-throttle system that will plug-in to existing throttle linkages.

So to apply the concept: actuator, cable, 3DOF accelerometer and ECU

ECU logic:
1. Program RPM (6000rpm)
2. RPM Sensor (compares current rpm to 6000rpm)
3. Are we above set rpm? (If yes, release throttle cable/If no pull throttle cable)

The above method that would only work for hull exit/rpm redline, but it's missing the re-entry portion. That's because rpm is a secondary data point. The primary data I need is what you just mentioned.

Quora: What components are needed to create a marine auto-throttle system (throttles to zero when hull launches off wave)?

Very cool! Never heard about that product before. I'm looking for a similar system for twin outboards though. Heard of any?

Source:
http://www.offshoreonly.com/forums/g...ear-later.html
http://www.boatingmag.com/gear/drive...imiting-clutch
http://www.marinedesigncorp.com/our-products.html

Re: strain gauges, these guys were at PRI

http://tecatperformance.com/

But it might be easier just watching RPM and controlling electronic throttles . Logic would be something like:

1. If RPM suddenly spikes upward, reduce throttle to maintain the RPM that occurred just before the spike
2. When RPM suddenly spikes downward increase throttle to maintain the RPM that occurred just before the spike
3. Throttle movements by the throttle man always override computer
4. Computer control is over ridden if the boat isn't flying level

This logic isn't tied to a specific rev limit and would be applicable to rough conditions that prevent top speed/RPM. Not bouncing off the limiter either. I would think that any ECU is sampling RPM at the rate you need.

There are aftermarket traction control systems that do something similar but they use ignition retard instead of throttle movement.

http://www.moretraction.com/Products_Drag_EFI.htm

Ignition retard might react faster than the actuator in an electronic throttle, but for long "flights" throttle control is definitely preferable.

Good luck with your project!