Tachometer - will it work with points?

[sastanley]

So, will my $30 automotive tach work with an ignition system with points?

It seems to, but the tach has also been in a box for years and seen some abuse..but before I run out and buy another $30 tach, I thought I should check..maybe I should dump that $30 towards the MMI electronic ignition kit instead

[sastanley]

The answer I got from a buddy with more electrical experience than me is, 'yes, it should work just fine.'

So, maybe I'll head down to the boat and hook up the new tach so I can see what's going on, an how things are running with some actual numbers.

[sastanley]

Ok, so my old tach was probably toast.

I bought a $30 Sunpro tach from my local auto store, and hooked up the green to the negative terminal on the coil, and hooked up +12 and ground appropriately, and received a nice rock steady tach reading. Now I have to figure out somewhere to mount it besides taped to the galley countertop

Just thought I would follow up so if someone else reads this thread a while from now, it is all buttoned up.

[jayw]

Thanks for the update, I've been wondering how to hook up my $30 Sunpro tack!

[s/v Dearbhail]

Funny you mentioned the SunPro tach. My boat came with no instruments, so to get a fast and inexpensive set of gages I used the SunPro tach, temperature and oil pressure gages. They worked great!

[agraziano23]

What kind of senders did you use? how did you connect them to the engine?

[sastanley]

agraziano -

In this case, the SunPro tach has 4 wires (hopefully I remember all the colors):

Red - (+) to 12 volt for instrument power (i simply went to the coil (+), but any 12 v source is OK)
black - (-) to engine/boat/busbar/12 v ground
green (-) to negative side of coil (this apparently picks up the coil energizing to provide an engine speed on the tach)
white - (+) backlight

*note on the light- I sent mine to the (+) on the coil as well. I figure in the moist environment, a light on whenever it is operating will help reduce moisture inside the tach..no sense in making it complicated up to the running lights or steaming light.

* One other note - Since originally posting this thread, I've gone to electronic ignition & a new coil (the original coil heated up & failed after about 60 minutes of use)..they have had no bearing on the tach's effectiveness

[Rick_Powers]

I am a big fan of the cheap auto tach alternative.

The only issue is that the MMI tach has a smaller upper scale (4K rpm) for better resolution (if you need it) compared to 8K for a cheap auto tach.

What I have learned is that "full speed" is "full speed" regardless...