Tachometer for '72 1150

[monk-monk]

I want to purchase a new tach for my '72 1150...thunderbolt ignition...what tach should i be using..?

 

[Chris1956]

Re: Tachometer for '72 1150

Most any aftermarket OB tach will work on that motor. You need to look to see if there is a brown wire on the switchbox, on the non distributor side. That is the tach signal wire and it is set up for the old Merc tachs, which no longer exist(or are hard to get). If so, that needs to move and connect ro one of the yellow stator wires, at the rectifier.

 

[monk-monk]

Re: Tachometer for '72 1150

Thanks for the info chris...I actually have the original tach and a NOS mercury tach of the same style (they are the older 70's Stewart Warner gauges) and yes, my switchbox has the brown wire terminal as you described...SO, the first thing i need to do is get my existing tach connected to one of the stator terminals at the rectifier! Right now im running the NOS Tach connected to the front of the MerCrontrol, i had the boat out Monday and it runs great...until i get to 4000rpm's then it goes into a preignition or detonation mode (sounds like spark knock or chattering)...im trying to figure out whats occurring at the 4000rpm level because i still have more throttle available at the controller..and i don't believe im getting all my top end out of it...

 

[usskydvr]

Re: Tachometer for '72 1150

Make sure your timing has no more that 21 degrees total advance. (Spec says 23, but that was in the old days with higher octane gas)