Folow up on engine Rev Counters ...

[Refueler]

Literally regardless of engine - if it has an alternator - this should work.

www.ebay.co.uk/itm/295054713247

Its a sensor that you strap to the outside of the alternator - it then senses the rotation and sends out pulses based on the RPM of the alternator. The meter can be adjusted to suit the pulses ..

www.ebay.co.uk/itm/295017036061

I have received the above and will be fitting when weather improves.

Having seen the prices of various gear to show engine RPM and the 'marine' prices .... I just had to give this a shot !!

 

[GHA]

or diy option - I've PCBs with a yet untested RPM circuit but someone else has it working >

Needs a few quids of components, esp32 or arduino plus a few lines of code & a Win laptop or Pi running signalk then it's all graphed with every other piece of data.

 

[Tranona]

Used one of these for many years. ebay.com/itm/Small-Engine-TACHOMETER-Treysit-Sirometer-Vibration-Tachometer-OEM-Tecumseh-Tool/264580371612 standard issue at British Seagull!

Easier to use for a single cylinder like the Yanmar 1GM, but once you get the hang of it can be used on multicylinder engines.

 

[Buck Turgidson]

Just get a phone app. Plenty available. Or call one of my old acoustic AEOp mates and they will tell you the engine RPM and prop speed by ear. ???

 

[AngusMcDoon]

or diy option

I did one a decade ago...

https://forums.ybw.com/index.php?threads/yapp-home-made-diesel-tacho.317240/

which was a rejig of a petrol engine one that inductively detected the spark from the HT line...

https://forums.ybw.com/index.php?threads/yapp-diy-outboard-rev-counter-and-hour-meter.277354/

 

[GHA]

I did one a decade ago...

https://forums.ybw.com/index.php?threads/yapp-home-made-diesel-tacho.317240/

which was a rejig of a petrol engine one that inductively detected the spark from the HT line...

https://forums.ybw.com/index.php?threads/yapp-diy-outboard-rev-counter-and-hour-meter.277354/

???
Pretty sure I would have visited those for shameless looting researching the circuit above. ?
mpu9259 compass modules have cleared customs here after only 9 days from aliexpress order, will be nice if a rev counter could also give fast compass data ?

 

[Refueler]

Just get a phone app. Plenty available. Or call one of my old acoustic AEOp mates and they will tell you the engine RPM and prop speed by ear. ???

I have a Phone App that uses Doppler sound effect to measure speed of passing planes / cars etc.

I have a magnetic bicycle meter .... glue the magnet to flywheel, position sensor so magnet passes it close ... works on same principle as impeller log. Problem with the bicycle meter is its set for 26 / 27" wheel and distance ... not rpm.

What I like about the items I linked to in opening post - the simplicity of fit and set-up. Just strap it to alternator ... mount the dial ... connect a few wires. Not only RPM - but Hours Meter as well.