Motor Control Circuit With Stop Limiter And Position Sensor Readout

I'm not sure what suggestions you're looking for - unless you're asking if relays are better than simple switching - then, Yes. Your relay circuit is fine - it will run the motor in whichever direction you flip the switch.

Your (normally closed contact) limit switches should go in the green and blue lines from the switch. Obviously, the "Up" limit must go in the line that controls the "Up" direction and vice versa. It's not possible to say which way the motor will turn, from your schematic. So simply swap the motor wires if it goes the wrong way when first wired up.

Since your position sensor will likely be completely independent of the motor control it doesn't make any difference here.

Another option, which would fit well under the previous $500 expense, would be to link the pivot of the jet ski's trim to a potentiometer (variable resistor) and drive your trim motor as if it was a servo. Then you would control it with another potentiometer and the trim would just tilt to whatever you dialed up on your control. This kind of simple control is called a bang-bang servo (full voltage either way or off, not modulated according to position error) and works very well for simple positioning control - the main advantage for your application is that you don't need an eye on the position indicator. Set the trim dial and the automatically activated relay will drop out when the position of the pivot potentiometer reaches the same (within a selectable tolerance) as your controlling one.

 

550HP ?!! Eeek! On a jet ski?! Are you kidding me?

What does the trim motor look like? Now I'm imagining it's some kind of hydraulic hybrid. Do you have any data, if it's actually an electric drive? Photos would help a lot. It sounds like your system must already have an encoder or resolver built-in for reporting back the trim position. Details on that would be important too.