which tach for thunderbolt ignition?

[chrishayes]

I have a 1974 1500 and the maual says to only use a tack that is stated to work with the thunderbolt ign system. What type tach should I look for? Will any other types work?

 

[Chris1956]

Re: which tach for thunderbolt ignition?

Chris, you have two choices. You may use a standard aftermarket universal outboard tachometer, and slightly alter the engine wiring or you you can try to locate a proprietary merc tacho from the early 70s and use it without modifing the wiring.

I recommend the former plan. To alter the wiring on the motor, move the brown wire from the starboard side of the switchbox to either of the yellow wires on the rectifier. Now hook up any aftermarket tach, using the directions for your merc and set the selector switch on the tach to 12P.

 

[chrishayes]

Re: which tach for thunderbolt ignition?

Well, it doesnt matter to me whether I have to modify the wiring as there is nothing there as it is. The rectifier is long gone and the stator wires are corroded up inside the stator housing, so all wiring and parts will be new and wired by myself. Thanks a lot, I will be going with an aftermarket tach.

 

[TopGunn]

Re: which tach for thunderbolt ignition?

I moved the brown wire like he stated and my aftermarket tach works fine on my thunderbolt

Thanks Chris

 

[chrishayes]

Re: which tach for thunderbolt ignition?

is this a thread with all Chris's?? Cool!