How to: rig some kind of tach to vintage big twins?

[dem45133]

Will be doing a twin installation of two vintage (a '59 35 and a '62 40hp) on a 27 foot sailboat... I'd like to figure out some generic tach setup (low end automotive maybe?) to monitor prop pitch changes and best fuel econ study. (twin install is not for power... just for redundancy on great lakes waters). Any ideas?

Dave

 

[jimg984]

Re: How to: rig some kind of tach to vintage big twins?

use auto type and come off the coil on the dist side to the tach and ground the tach

 

[ezeke]

Re: How to: rig some kind of tach to vintage big twins?

You could use a TinyTach for that: http://www.tinytach.com/tinytach/index.php

I've attached a photo of one on my kicker.

They have a built-in battery and you just need to wrap a built-in wire around a spark plug wire to get the signal. It also can have a hour meter built in.
Be sure to ask for the correct one for your motors if you want to try it. You cannot lengthen the wire, they have to do it when you order.

 

[dem45133]

Re: How to: rig some kind of tach to vintage big twins?

Thanks, I checked out the tiny tack. Looks like something there will work. If I remember right... the old Evinrude big twins only create one spark per revolution on each of the two independent ignition systems... Only one magnet in the flywheel passing independent coils triggered by separate point sets situated 180 from each other?.

Thanks.

 

[CATransplant]

Re: How to: rig some kind of tach to vintage big twins?

use auto type and come off the coil on the dist side to the tach and ground the tach

Sorry, but no. The engines he is talking about are pure magneto. There is no distributor. You need an inductive pickup for a tach for the big twins.

 

[F_R]

Re: How to: rig some kind of tach to vintage big twins?

Thanks, I checked out the tiny tack. Looks like something there will work. If I remember right... the old Evinrude big twins only create one spark per revolution on each of the two independent ignition systems... Only one magnet in the flywheel passing independent coils triggered by separate point sets situated 180 from each other?.

Thanks.

That's right. 2 independent ignitions, each firing once per rev.

 

[byacey]

Re: How to: rig some kind of tach to vintage big twins?

Here's something we experimented with awhile back, worked out quite well:
http://shareaproject.com/pages/projectThumbs,p,411,00.html
and:
http://forums.iboats.com/showthread.php?t=106719&highlight=Black+Box