SteadyPass - DIY boat speed control kit

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Linear servo option. 
I was attracted by linear movement, and good precision.

Worked perfect!  0.2mm position accuracy, no dead-band on positioning.  Also - stall protected, does not overheat. Just not sure it is robust enough.

It needs less clearance around rod, but actually takes more of rod's lenght.

update:

currentrly seems to be the silver bullet of servo options, for all engines.  Yet have to test on EFI type engines (different mount than merc 3.0)

RC servo - controls throttle.

Benefits
1 - Cheaper, replacement parts are widely available for self service
2 - Easy to control
3 - One can make it himself for $15 cost

4 - No bendy/sticky cable to worry about

5 - Simple

Downsides
1 - Requires adjusting throttle rod and/or servo zero position when installing

2 - Limited travel, requires to set throttle handle close to needed position, won't handle lower speeds if handle set to 100% throttle position.

 

Video of how proto 0.5 works.

https://youtu.be/tnYShy6vqc4

SAFETY first.  Servo is operating so that it can NEVER increase throttle, above what you have set by your throttle handle. And when you return handle to neutral - it will force power to neutral. No other options. ESPECIALLY important when you, the mighty owner, is handing on the other end of ski rope.

Kit can support various inputs, for example - digital temperature sensors DS18, which are $2-3 on ebay.  You can measure temperature inside engine bay, outside air, water, even cooling fluid and oil, with a bit of DIY install of that waterproof sensor.  Analogue sensors can also be supported.

What else can make this kit better?

Arduino 16MHz - is the computing heart of the system. Measures current speed, controls LCD, allows to change set point, and even keeps some statistics going.   All the secret sauce is in the code, which indeed, the most difficult part.

Engine RPM is measured  at input of your standard tachometer, which is hooked up to negative lead of ignition coil.  Optical decoupler is put between tach signal and compute module.  Setting for 4/6/8 cylinder is available.