Easiest way to tach my motor

[Keegan.MW]

I need to figure out what rpm I'm running because I'm in the market for one or two new props. My boat setup is a 18' flat bottom with a 35hp 1978 Johnson seahorse. I've heard to just wrap the tach wires around the spark plugs but I have no idea what this means.. Can someone walk me through what I need to do specifically and maybe give me a link as to what specific tach will be the best to buy for this application? Thanks for any and all advice!

 

[Texasmark]

Re: Easiest way to tach my motor

My lawnmower has a tach. Can't cost much as it's on a lawnmower. I think the brand is "Tinytach". Sense wire wraps around a spark plug wire. May have to adapt to a 2 cycle vs a 4 cycle. But some 4 cycles fire every rev even though the piston is in the exhaust stroke....flywheel magneto will do that. If so no biggie. Otherwise if it's obvious it's off by a factor or 2 or 1/2 just improvise.

Mark

 

[Sea Rider]

Re: Easiest way to tach my motor

Would recommend Hardline hour/tachs, get the programmable fire model. Follow instructions, ease of installation. The pic corresponds to the Tiny Tach model, which uses a ground wire. Hardline doesn't need a ground wire, just wrapp 3-4 cable turns on any spark plug cable and secure with tape, tie wrap. You must know the firing sequence of that engine for tach to read accurately.

Happy Boating

 

[jestor68]

Re: Easiest way to tach my motor

Just buy a Tiny Tach and follow the included instructions(with pictures).

 

[1FASTLASER]

Re: Easiest way to tach my motor

+2 on the tiny tach..simple,accurate,inexpensive

 

[Scott Danforth]

Re: Easiest way to tach my motor

if you want it installed to keep track of RPM's all the time, install a tiny tach

if you just need to check the RPM's once, I would use a volt-ohm meter that registers frequency then convert the frequency to RPM. my meter also has PPM (pulses per minute)

 

[Sashav]

Re: Easiest way to tach my motor

The Tiny Tach would be my choice, you can find it under 50$ on ebay it comes with instructions how to use it.

 

[Sea Rider]

Re: Easiest way to tach my motor

Sorry, TT has design issues, the hard red cable that wraps around 3-4 turns on the spark plug cable with use and engine vibration will end braking where it meets to ground connector. Hardline tachs has just one flexible pick up wire that can be cut to size once cable has been conveniently routed. You decide....

Happy Boating