Capt Robbie,
Your second and third pictures are shots of the "cable brake". It is designed to put pressure (friction) on the inner cable and keep the throttle from creeping.
On my 3GM30F, the throttle would creep so badly that I had to constantly hold it at the speed I wanted for the entire trip. It was extremely exhausting just coming into or out of the harbor AND I could not get any speed over 2200 RPM.
You seem to be describing somewhat of the same issue and placement.
I should say at this point, I did have to replace my cable, as I found the outer covering was cracked and broken open in 2 places along the run and under the Cable Brake itself. Dry rot, I assume.
The Cable Brake (in your picture) looks like it is down in the engine compartment also. It really belongs up closer to the throttle handle assembly. Down where it is, at least on my cable, causes the entire cable to flop around and you don't get a smooth sliding and loss of control at the engine.
You can see this for yourself if you go inside the cabin just under the wheel and have someone move the throttle back and forth. The movement may or may not be much but it will effect the control. Once I moved it up to just under the throttle handle at the wheel my problem went away and I increased RPM's.
Try loosening the bolt and take it off the cable where it is and bring it up to about 6 - 10 inches from the base of the throttle assembly at your wheel.
I think you'll find the the "looseness" you are describing will go away and the handle will hold in any position you want.
You'll have to adjust the tightening of the bolt to get the handle to move freely and still hold in position. The speed should come up also to get you closer to 3000 RPM.
I hope this helps with both issues, it will at least eliminate the throttle creep.
I posted photos in my albums you can look at to see the Cable run.
